FISHES’ EGGS it 
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 hooklets 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 their 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 ege. These are globular in shape, and merely consist 
of a large yoik encased in a delicate egg membrane, 
and are to be found in many very different positicns, 
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 egos, 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 
