Page:Popular Science Monthly Volume 19.djvu/128

118 if skin stimuli be cut off; 5. The direct action on the respiratory centers of the hotter blood of the heated animal is probably not, or not only, due to its temperature but to its greater venosity.

Dr. W. K. Brooks has an exhaustive paper entitled "Observations upon the Early Stages in the Development of the Fresh-Water Pulmonates," in which he discusses the works of Lankester, Fol, Rabl, Jhering, and others. The plates accompanying his paper are models of clearness.

S. F. Clarke follows with an interesting illustrated paper on "The Development of Amblystoma," which closes the number.

Part III, devoted to the work of the Chesapeake Zoölogical Laboratory during the session of 1878, begins with an account by Professor W. K. Brooks of the organization of the school, its location at Fort Wool, and the methods of study adopted. This is followed by lists of the plants and animals observed at Fort Wool—the former by Mr. N. B. Webster and the latter by Mr. P. R. Uhler. The next paper, by Dr. Brooks, is on the development of Lingula and the systematic position of the Brachiopoda. He succeeded in getting the free-swimming larva of Lingula at a stage similar to the one described by Professor McCready many years ago, and carried it through to the early stage of the adult form. It is useless to attempt to do justice to this valuable contribution without the plates which accompany it.

The other papers in this part are "On the Larval Stage of Squilla," by Dr. Brooks, and the "Description of Lucifer Typus," by Walter Faxon.

Part IV contains a paper of great scientific and economic value, on the development of the oyster, by Dr. Brooks. German and French authorities had stated that eggs of the oyster were fertilized within the body of the parent, and were carried by them until they had reached an advanced stage of development, when, provided with shells of their own, they were discharged, and swam freely in the water until they became attached. Misled by these statements, Dr. Brooks had failed the season before in securing any results. On the 15th of May he commenced operations by opening oysters every day throughout the breeding-season. His success in artificially fecundating the egg was remarkable. Millions of eggs were fecundated with but little trouble. He traced their developmental history from the segmentation of the egg to those stages already described by European naturalists. He found the female oyster in various conditions: some in which the ovaries were largely distended, and the eggs fairly oozing from the oviducts; others in which the ovaries were half filled, and others still wherein the ovaries were quite empty, and in no case did he find a single fertilized egg in the ovary. Dr. Brooks emphatically says that, so far as the oyster of Chesapeake Bay is concerned, "the eggs are fertilized outside the body of the parent, and that, during the period which the young European oyster passes inside the mantle cavity of its parent, the young of our oyster swims at large in the open ocean." A very clear description is given of the anatomy of the oyster, as well as some practical points in regard to their artificial fecundation. A careful estimate shows that an average sized female oyster contains about nine million eggs; an unusually large oyster may contain as many as sixty million eggs.

Dr. Brooks's investigations have a very practical bearing on the question as to the final exhaustion of the natural oyster-beds on our coast by unlimited dredging.

One would naturally think that with such remarkable fecundity the question of extermination need be hardly entertained, but the eggs after fertilization, if left unprotected, meet at every moment of their existence enemies who devour them, and, when at a later stage they rise on the water and form a film on the surface, fishes devour them by millions. Dr. Brooks has shown that if the egg is not immediately fertilized it soon perishes, and of course in its natural home the chances of its fertilization are infinitely less than in the artificial method actually tried.

In a recent paper by Dr. Mobius a long table is given showing the number of oysters taken yearly from the Bay of Cancale, on the coast of Norway, during the last hundred years. Dr. Brooks reproduces this table, to show that unlimited dredging has greatly reduced the production.

Without detailing the process here, Dr.