96 Proceedings of Societies. 
’ 
therefore, pelagic. Those eggs which are heavier than water and would fall to the 
bottom and, in many cases, die in the mud, are provided with various contrivances 
to attach them to foreign substances as soon as deposited. In the herring, this 
consists of a membrane overlying the zona, which becomes extremely viscid when 
it is deposited, and causes the eggs to adhere to any substance with which they may 
come in contact. In thesmelt (Osmerus), an outer membrane exists, which is at- 
tached to the zona only around the micropyle. At the time of spawning this mem- 
brane is stripped off and attaches itself to foreign substances, thus suspending the 
egg by the micropylar region. In the gobies, a network of threads similarly at- 
tached to the zona takes the place of the outer membrane in the smelt. In the 
sticklebacks a number of mushroom-shaped processes, attached to an outer mem- 
brane, are viscid. 
There are in many eggs long threads attached to the zona, which twine about 
sea-weeds, etc., and suspend the eggs. These threads vary greatly in different eggs. 
In /sesthes they are massed on one-half of the zona, and form a cushion by which 
the egg is attached. In the mud minnow (/2ndu/us) the threads are numerous, and 
mere prolongations of an outer thin membrane. In Atherinopsis they are fewer (10), 
with hollow bases which fit into projections of the zona. In the flying fish and gar 
fish they fit into pockets of the zona radiata. 
All the membranes and processes were shown to be the product of the egg itself, 
and in those eggs provided with processes these are usually developed before ans 
zona makes its appearance, 
In the yellow perch a thick covering overlies the zona. This differs from all 
other structures in the fish eggs. It is the product of the granulosa cells overlying 
the zona, and is not formed until the latter has almost attained its full thickness. 
It was further shown that the granulosa cells are modified in the region of the 
micropyle, and one large cell usually acts as a plug to the micropyle in ovarian 
eggs. 
