428 American Work in the Department of [June, 
luscoida are related, but that they are connected so closely that 
the advisability of such a division is very doubtful.” 
en years ago many crudities, due to the defective state of our 
knowledge of the development of the Invertebrata, obscured the 
relations of many forms now more or less thoroughly understood. 
At that time the present writer took strong ground in favor of a 
position essentially similar to that which more lately has received 
the support of Prof. Huxley, and which the labors of Brooks 
have more thoroughly elucidated and now placed on a firm basis. 
As this position was vehemently contested at that time by Prof. 
Morse, and was considered by other good naturalists as somewhat 
unsafe, it is with more than ordinary pleasure that the writer now 
records the latest step of progress which, while it has corrected 
many of his own misconceptions, has resulted in proving the 
essential correctness of the main features of his hypothesis of 
that earlier time. 
It is hardly necessary to add that the Tunicata, then left by 
both Morse and himself, as well as the great body of naturalists, 
in the company of the Molluscoida, have since been effectually 
divorced from them, and may be said to have hardly found even 
yet, with relation to other invertebrates, a definite location. 
The second paper of Prof. Brooks on “ Preliminary observa- 
tions upon the development of the marine prosobranchiate Gas- 
teropods,” concerns the early stages of Astyris and Urosalpinx, 
and comprises an abstract of observations, with one plate. 
Still another report on important biological work in this depart- 
ment, is Prof. Brook’s “ Abstract of observations upon the artifi- 
cial fertilization of oyster eggs and on the embryology of the 
American oyster.” Am. Fourn. Sci, xvii, No. 108, December, 
1879, pp. 425-427. 
Important differences of breeding habits are pointed out be- 
tween the O. virginica of America and the O. edulis of Europe. 
The eggs of the American oyster are fertilized outside the body 
of the parent, and the young swim at large during the period in 
which the fry of the European species are sheltered in the mantle 
cavity of the parent. At the breeding season each individual adult 
contains only eggs or spermatozoa. Segmentation is completed in 
about two hours, and follows substantially the course described 
for other Lamellibranchs by Lovén and Fleming. 
The oldest ones which could be raised were almost exactly 
