1006 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [6] 
various ages. Special attention should, however, be paid to young oys- 
ters, and to the development of the generative organs in these. <As far 
as ny observations go, exclusively male or exclusively female oysters 
do not occur. In full-grown, healthy oysters an oval lump of sperma- 
tozoa may be observed, surrounded by free eggs placed radially and with 
great regularity. In comparing perpendicular and other cuts, these 
eggs appear in close elliptically-shaped groups or lumps, each in a tissue 
pouch, or several together in one and the same pouch. The eggs are 
generally attached by a wide base; are granular, and provided with a 
large, round nucleus and nucleoli. In specimens stained with fine picro- 
carmine the difference between the nucleus, with its appurtenances— 
sit venia verbo—and the egg-cell itself can be very distinctly observed. 
The egg-cell has a brownish-yellow color, and is granular, whilst the 
nucleus is reddish, and appears to be a homogeneous body. In oysters 
which have already lost some of their young spat, the empty pouches 
or hulls may be seen in considerable number. As far as my observa- 
tions go, I am inclined to think that eggs and spermatozoa do not mature 
simultaneously. It seems that new generative products may at a later 
period be developed in the empty pouches. It would be worth the 
trouble to examine into this matter carefully. 
My preliminary observations have convinced me that it is absolutely 
indispensable to the success of these investigations to make a series of 
sections of oysters of different ages and examine these carefally~ If 
during the coming year I am privileged to continue my investigations, 
I shall principally follow this method. 
The investigations relative to the history of the development of the oyster 
are perhaps farther advanced than any other portion of our investiga- 
tions. They were in charge of Dr. Horst and Professor Hoffmann. Mr. 
Horst made use of the booth of the zoological station at Wemeldinge, 
described in the first part of our report; and his observations were so 
successful that he was enabled to prepare a brief review of the embry- 
ology of the oyster, accompanied by the necessary illustrations. This 
review is too extensive, however, to be embodied in this report, as a 
whole, and we shall therefore give its principal features in brief outline. 
It is particularly difficult to obtain the necessary facts relative to the 
first stages of the development of the oyster; and it is hoped that next 
year’s observations will supplement those of the present year. The 
principal difficulty lies in the circumstance that, as a general rule, more 
female (mother) oysters are found with old than with quite young brood. 
There is no doubt that, in their general features, the first stages of the 
development of the oyster-egg resemble those of other bivalves. The 
result of the first stage in the process of development is, that the lower 
(vegetative) pole of the egg is formed of a large granular cell from which 
the entoderm* (and mesoderm ?) develop, whilst on the upper (animal) pole 
numerous smaller cells may be observed which furnish the material for 
*T have retained two terms, which are not found either in Webster's Dictionary or 
in Dunglison’s Medical Dictionary, and which—not being Dutch, but Greek—will be 
