phila supply in themselves all the evidence that even an extreme selectionist should ask. To explain why large changes are observed as well as small ones it is suggested that we may be "witnessing the disintegration of highly developed apparatus instead of its building up."

Dr. Castle's contribution also deals with the controversy over the nature of evolutionary change, whether continuous or discontinuous. He, however, is less inclined than Dr. Jennings to resolve the differences between the two schools into differences in the use of terms. After allowing for the effects of the confusion in terminology, he sees "two contrasted sets of ideas," which he arranges under the headings Darwin and DeVries.

Students of paleontology, geographical distribution and classification are shown, in general, to favor the belief in gradual evolution and the efficacy of selection. The opposite view, that of discontinuous variation and stability of new forms, is held by a majority of the students of experimental breeding. Support of the former view by one who has done such thorough work as an experimental breeder must have great weight.

From the point of view taken by Jennings, it would seem that in contrasting the mode of origin and the stability of new types Castle is himself open to the criticism of using the term "type" ambiguously. If by a new type is meant anything new, most geneticists would range themselves with DeVries, but if a new type is something more comprehensive, DeVries and his followers must stand alone.

The crux of the difference between Castle's views and those of practically all classes of mutationists would seem to be in Castle's holding that selection determines in some measure the range of variation in subsequent generations. Confining the question to inherited variations, does the selection of extreme variations form new centers of distribution? To do so, it would seem that small variations must be more numerous than large ones, an assumption which would be ques

tioned by most mutationists, including Mor

gan.

Although cases were encountered in Dr. Castle's own work in which selection gave no tangible results, in many characters progress was rapid and continuous, with no indication of other than physical limits, and it is held that in the smaller mammals, which Dr. Castle has studied intensively for many years, there are few characters which can safely be referred to the agency of perfectly stable genes.

That selection does, from a practical standpoint at least, produce results is abundantly shown by Dr. Castle's work. If by the use of refined reasoning his critics are able to show that change in a single Mendelian character is not the only possible explanation of the results, these critics may then be referred to Jennings's results with Difflugia.

Dr. Riddle has here brought together in a concise and readable form the results of his extensive experiments on the nature of sex in pigeons and has coordinated these results with the work of other investigators.

Sexual differentiation is interpreted as the expression of quantitative differences in the rate of protoplasmic activity; the more active metabolism resulting in males, the less active in females. Many lines of evidence are presented, all of which are consistent with the view that preponderance of one or the other sex is conditioned by the rate or level of metabolism. These various lines of evidence show the following characteristics to be associated with the female sex, all of them being associated also with a low level of metabolism: Large size of yolk, low per cent. of water in the yolk, high per cent. of stored material, high total stored energy, exhausted physical condition of the mother, age of the mother.

In crosses the percentage of males increases with the width of the cross to the point of infertility. Since males are characterized by a more active metabolism, there is an agreement between these results and the commonly observed increased vigor of hybrids.

Assortive mating of gametes and differential death rates are fully considered and neither

is found to furnish a possible explanation of the controlled sex ratios.

Not only can the sex of pigeons be changed but it can also be accentuated. The females hatched from the second egg of the clutch, laid in the autumn by overworked birds, are more pronounced females than the normal females of the species. This is evidenced by the persistence of a right ovary in such birds. In normal female pigeons the right ovary has completely degenerated in the week-old squab.

The literature reviewed gives evidence of a relation between rate of metabolism and sex in a great variety of animals, varying from worms to man. With sex viewed as an expression of differentiated metabolic activity, its independent origin in diverse groups of organisms ceases to be a stumbling block, being no more remarkable than that the same color should have originated independently in different groups. The work reported is confined to the animal kingdom and it should be of interest to determine whether in diœcious plants there is a corresponding differentiation in the rate of metabolic change.

Dr. Riddle's work would seem to call for discussion by those students of genetics who place the distribution of the chromosome in a causal relation to sex, since his results directly challenge this interpretation. It is shown that in some cases at least sex is determined before the segregation of the chromosomes, a fact which would seem to make chromosome number a characteristic rather than a cause of sex.

Furthermore, the challenge extends to all Mendelians, for if "one hereditary character (sex) is modifiable, is of a fluid, quantitative, reversible nature," surely the alternative nature and stability of other characters come in question.

It is worthy of note that all three investigators, though working in widely separated fields and approaching the problem of evolution from very different angles, conclude that evolutionary change is, in effect at least, a gradual process that is not beyond the power of man to man influence.

G. N. COLLINS

SPECIAL ARTICLES

THE ROLE OF CATALASE IN ACIDOSIS IF an inorganic acid, such as hydrochloric. be administered to an animal, it is neutralized by the alkalies of the blood and tissues; if an organic acid be administered, it is oxidized, unless the oxidative processes of the animal are defective, as in diabetes, in which case the organic acids are neutralized, as are the inorganic. This neutralization of acids leads to a depletion of the "alkaline reserves" of the body, which produces the condition known as acidosis. By the term acidosis is meant the impoverishment of the tissues and blood in alkalies. In very severe cases of diabetes, the animal is not able to burn sugar and can burn fat and protein only as far as ẞ-oxybutyric and diacetic acids and acetone, hence the tissues of the diabetic would become acid in reaction were it not for the fact that the acids formed in this disease are neutralized by the alkalies of the tissues. Since this neutralization leads to a depletion of the "alkaline reserves" of the body in severe cases of diabetes and since acidity of the tissues is incompatible with life, the animal dies. From the foregoing it is readily understood how the intravenous infusions of sodium bicarbonate are helpful in overcoming the coma of diabetes. Besides diabetes, it is known that acidosis occurs in "surgical shock," in anesthesia, and in starvation. It is also known that in these conditions oxidation is decreased and that the accumulation of the resulting incompletely oxidized substances, acid in nature, are responsible for the acidosis. The present investigation was carried out in an attempt to find an explanation for the decreased oxidation with resulting acidosis in the conditions mentioned.

Diabetes.-Pancreatic diabetes. was produced in dogs by extirpating the pancreas. Sugar appeared in the urine a few hours after the operations. About two weeks later, when the animals were in a moribund condition, they were killed and the blood vessels were washed free of blood by the use of large quantities of 0.9 per cent. sodium chloride, as was indicated

by the fact that the wash water gave no test for catalase. The tissues were then removed and ground up separately in a hashing machine. The catalase of one gram of the different tissues was determined by adding this amount of material to 50 c.c. of hydrogen peroxide in a bottle at 22° C., and as the oxygen gas was liberated, it was conducted to an inverted, graduated vessel, previously filled with water. After the oxygen gas thus collected in ten minutes had been reduced to standard atmospheric pressure, the resulting volume was taken as a measure of the amount of catalase in the gram of material. The material was shaken in a shaking machine at a fixed rate of 180 double shakes per minute during the determinations. It was found that the catalase of all the tissues of the diabetic dogs was decreased, the greatest decrease being in the heart and liver. The catalase of the heart was decreased by about 48 per cent. while that of the liver was decreased by about 72 per cent.

son observed that oxidation was decreased in

"surgical shock" with resulting acidosis.

Cannon has shown that in man in conditions of traumatic shock there is a condition of acidosis which is relieved by injections of solutions of sodium bicarbonate.

Anesthesia.-The anesthetics used were ether, chloroform, chloral hydrate, nitrous oxide, and magnesium sulfate. The animals used were cats, dogs, and rabbits. The ether and chloroform were administered by bubbling air through the respective anesthetics in a bottle, which was connected by a rubber tube to a cone adjusted over the snout of the animal. Chloral hydrate anesthesia was produced

by the introduction into the stomachs of rabbits of 10 c.c. of a 2 per cent. solution of chloral hydrate per kilo of body weight. A mixture of nitrous oxide and oxygen in the poportion of one to five was administered to cats in the production of nitrous oxide anesthesia, while magnesium sulfate anesthesia was produced by the subcutaneous injection of 7.5 c.c. of a 20 per cent. magnesium sulfate solution per kilo of body weight. It was found that the catalase of the blood was decreased by all of these anesthetics and that the extent of the decrease was proportional to the depth of anesthesia. Chloroform and nitrous oxide, in keeping with their rapid action as anesthetics, decreased the catalase of the blood very quickly, whereas chloral hydrate and magnesium sulfate, in keeping with their slower action, decreased the catalase much more slowly, while ether occupied an intermediate position in this respect. It is recognized that there is a decrease in oxidation with resulting acidosis in anesthesia and that this is more likely to occur with a powerful anesthetic, such as chloroform, than with ether.

Starvation.-Four rabbits were used in this experiment. Two of them were killed before the period of starvation was begun, and after washing the blood vessels free of blood, the catalase of the different tissues was determined according to the method described in this paper under "diabetes." The remaining two rabbits were starved for six days, and at the end of this time the catalase of the tissues was determined in the same manner as that of the unstarved rabbits. It was found that the catalase of the voluntary muscles was decreased during starvation by 40 per cent.; that of the fat by 70 per cent.; while it remained normally high in the heart.

The conclusion is drawn that the defective oxidation in diabetes and the decreased oxidation in anesthesia, starvation, and "surgical shock "with resulting acidosis is propably due to the decrease in catalase, an enzyme found in the tissues and possessing the property of liberating oxygen from hydrogen peroxide. W. E. BURGE PHYSIOLOGICAL LABORATORY OF THE UNIVERSITY OF ILLINOIS

THE CONTRIBUTION OF ZOOLOGY TO HUMAN WELFARE1

AT the Philadelphia meeting of the American Association for the Advancement of Science, Convocation Week, 1914-15, there was held, under the auspices of the American Society of Naturalists, a symposium entitled "The Value of Zoology to Humanity." I was, unfortunately, very busy with the affairs of the general association and was unable to attend this symposium. There were four papers presented. The first of these is printed in SCIENCE for March 5, 1915, and is entitled "The Cultural Value of Zoology." The address was given by Professor E. G. Conklin, of Princeton. It is a very readable address, full of interest, containing much of that delicate humor characteristic of Professor Conklin, and possibly rises nearly to the exact height demanded by the title. But it is not a zoological address, in spite of its title. It is broader, and comprehends all biology. It is divided into two headings: (1) "Contributions of Biology to Education"; (2) "Contributions of Biology to Civilization." Under the first heading he dwells upon the immense enthusiasm and intense concentration of the biologist in his work, touching upon the evil effects of over-specialization. and referring to the few great leaders in biology who have become interpreters to the plain people-men like Huxley, Galton, Metchnikoff and Forel, who have applied the teachings of biology to social problems.

1 Read before Section F (Zoology) of the American Association for the Advancement of Science in a Symposium upon "The Contributions of Zoology to Human Welfare," Pittsburgh, Pa., December 31, 1917.

He then dwells upon the powers of observation and imagination of the biologist, and the unique place which biology occupies among all the sciences in its cultivation of esthetic appreciation and broad sympathies. He admits that these elements of personal culture are not absolutely distinctive of the biologist, and that "some good men in other fields are biologists gone astray."

Among the contributions of biology to civilization, he refers to the conquest of nature by all of the sciences, and suggests as a topic for general debate at the San Francisco meeting of the association, "Who built the Panama Canal?" feeling sure that biology would be able to show that it deserved "a large share of the credit." Without entering into detail, he states that, while biology is not generally considered the equal of physics, chemistry or engineering in its contribution to civilization, agriculture, animal breeding, bacteriology, experimental medicine, pathology, parasitology, physiology, sanitation, are all based on biological research.

It is the summary way in which Professor Conklin dismisses this aspect which, I think, weakens the effect of his address, for he goes on in his final consideration to the statement that "the highest service of science [mind you, science in general] to culture has been in the emancipation of the mind, in freeing men from the bondage of superstition and ignorance, in helping man to know himself." As a generalization this is fine, and he goes on to state that the doctrine of evolution which has revolutionized all our thinking regarding man and nature is the greatest contribution of biology to intellectual emancipation. His concluding paragraph is:

Biology has changed our whole point of view as to nature and man, and has thus contributed more than any other science to the emancipation of mankind.

Another of these four papers was read by Professor G. H. Parker, of Harvard University, and was entitled "The Value of Zoology to Humanity: The Eugenics Movement as a Public Service." Here again we have an extremely interesting and important article, from which we may quote the conclusion only:

To conclude, eugenics in the service of society is, in my opinion, entirely justified in demanding the sterilization by humane methods of those defectives who are in the nature of public wards, and this practise may be extended as experience dictates. Eugenics in its relation to propagating the best in the community has a fundamental position in that it is concerned through the elimination of the extremely unfit with the delivery of a reasonably sound stock for cultivation, but it is only secondarily connected with the final production of efficient members of society whose real effectiveness is often more a matter of social inheritance than it is of organic inheritance.

I consider Dr. Parker's address as a very valuable one, but, while showing what animal breeding has done, which may in a way be construed as relating to "the value of zoology to humanity," he uses this only as an indication as to what might be done with the human species; and, important as his address is, it is not directed specifically to the point at issue-the value of zoology to humanity.

The third of these addresses was by Dr. C. B. Davenport and was entitled "The Value of Zoology to Humanity: the Value of Scientific Genealogy." Here again we have a very important paper, written in Dr. Davenport's admirable manner. His argument in a broad way applies to the general field of biology, including botany, zoology and anthropology, and in a specific way to the human species. He refers to the complicated work of the animal breeders, and follows it with the statement,

And yet this precious human kind of ours, whose progress is so fatal to the world, goes its blind way, like any jellyfish, mates almost at random and