FISHES* EGGS 



fish's egg which was attached to the exhaust-pipe of 

 a tank in the Port Erin aquarium. 



Skates' and rays' eggs are similar in structure to 

 the egg of the dog-fish, with the exception that the long 

 fixing tendrils at each corner are replaced by four sharp- 

 pointed hooklets. These booklets take a temporary 

 hold of the moss-like seaweed on the bottom, and 

 soon the weed growing over the egg-case prevents it 

 being carried hither and thither by the tide. 



Dog-fishes' and rays' eggs are analogous in their 

 structure to the eggs of birds, except that they have a 

 horny insteady of a chalky shell. 



All sharks, dog-fishes, skates and rays have a carti- 

 laginous or gristly skeleton, and belong to one large 

 group of fishes. Many of then- young are born alive like 

 the young of animals, but when eggs are deposited 

 they are similar in character to those described. 



Turning next to bony fishes, such as the salmon, 

 the roach, and the plaice, we get quite a different type 

 of egg. These are globular in shape, and merely consist 

 of a large yolk encased in a delicate egg membrane, 

 and are to be found in many very different positions. 

 Some are heavier than water and lie on the bottom ; 

 some are lighter than water and float on the top. 



Of the heavier-than-water eggs, some, like those of 

 the salmon, are not attached to each other, or any 

 other object ; others, like those of the perch and roach, 

 are sticky when first deposited, and adhere to each other 

 or to rocks, stones, shells, and weeds. All freshwater 







