186 DEVELOPMENT OF FISHES 
and somewhat adhesive; they are deposited in “nests,” Z.¢, 
bowl-like depressions, and are attended by the male fish.* 
Other adhesive eggs are those of carp, Christiceps, Batra- 
chus. Eggs of Salmonids are deposited loosely in “nests” 
on a clean, gravelly bottom; their membranes are thick 
and parchment-like. On the other hand, the majority of 
pelagic fishes produce eggs which float (Figs. 196, 197) ; 
of these the membranes are extremely hygroscopic and 
transparent, and an oil globule, located in the yolk region 
of the egg, serves to diminish its specific gravity. The 
egg membranes of a number of Teleosts, e.g. Blennies 
(Fig. 199), appear essentially shark-like; a horn-like cap- 
sule is evolved, whose terminal processes afford it a firm 
attachment. Aberrant modes of oviposition are not lack- 
ing; the South American Siluroid, Aspredo, as is well 
known, carries its eggs attached to its ventral surface; the 
pipe-fishes and sea-herses, Siphostoma, Solenostoma, Hip- 
pocampus, have specialized a pouch-like fold of the abdo- 
men and of the ventral fins, which serves to retain the 
eggs and larve. It is curious to note that this remark- 
able condition occurs only in the made. 
The breeding habits of Teleosts are in general like those 
of Ganoids; their spawning season is usually during the 
spring and summer, but is seldom of very brief duration. 
The hatching of the eggs depends largely upon water 
temperature, and may vary from a few days to several 
months (Salmo). . 
B. THE FERTILIZATION PHENOMENA 
The processes of the maturation and fertilization of 
the egg have as yet shown but minor differences in the 
*In several genera they are carried about in the gill chamber of the male, 
thus ensuring aération. 
