Some Peculiarities of the Ova of Fishes. 83 



conditions are : i. That the egg be free and not adhesive, with a 

 thin membrane, and, 2, That it be immersed in water having a 

 greater density than 1.014. 



Among the fishes which produce floating ova may be mentioned 

 the cod, mackerel, Spanish mackerel, bonito, cusk, haddock, many 

 of the flounders, etc. A very curious and interesting contrivance 

 for causing ova to float on the surface, which otherwise would sink 

 to the bottom, is that resorted to by the beautiful paradise fish, of 

 China. The male fish constructs a floating raft by expelling from 

 his mouth bubbles of air coated with a fatty "secretion, which, 

 collecting on the surface, cling together, until a raft of viscid scum, 

 several inches in extent, is formed. After the eggs of the female 

 are deposited and fertilized on the bottom, in the usual manner, the 

 male collects them in his mouth and ejects them into this frothy 

 receptacle, which he keeps in constant repair, and preserves its 

 bouyancy by additional fatty bubbles, until the young fry are 

 hatched out, which occurs in about two days. Another method 

 for floating the ova is that of the Lophius, or goosefish — the eggs, 

 numbering about 50,000, are inclosed in a ribbon-shaped, gela- 

 tinous mass about a foot wide and forty feet in length, which floats 

 near the surface. 



Among the fishes which produce adhesive eggs are the little 

 black-head minnow [P. promelas~) and the goldfish. The male 

 black-head deposits the fecundated eggs singly upon the under side 

 of leaves of water plants and watches them unceasingly until 

 hatched. The ova of the goldfish are deposited singly upon the 

 weeds and mosses in a similar manner. 



The eggs of the yellow perch are held together in narrow strips 

 or ribbons of a glutinous character. Adhesive eggs of other 

 species, as the black bass, sunfishes, catfishes, etc., are deposited 

 in masses in shallow nests or depressions on the bottom ; and still 

 others deposit their spawn in variously-shaped adhesive masses 

 upon algai, roots and submerged objects. 



The eggs of the myxine, or hag, are oval in shape, enveloped in 

 horny cases and provided at each end with short filaments termin- 

 ating in triple hooks, by which they attach themselves to each other 

 and probably to foreign objects. 



Perhaps the most curious and bizarre of all fish ova are those of 

 the oviparous sharks and rays, which are quadrangular horny 

 capsules or cases, two or three inches in length, with long filaments 

 at the corners, which coil about sea weeds and other objects. 



