THE INFANCY OF FISHES 211 



band ; while the pointed end of the case terminates in a 

 pair of anchoring tendons. 



In the curious chimara or callorhynchus the egg assumes 

 a striking likeness to a piece of seaweed, and this is the 

 only known instance of such protective resemblance. 

 But stranger still is the fact that the egg, when laid, has 

 imperforate walls. Soon, however, certain areas of the 

 walls decay, forming a series of small holes which allow 

 of a current of water being drawn in by the growing 

 embryo in the fore part of the egg-sheath, and expelled 

 by the holes at the hinder end, thereby enabling the work 

 of respiration to be carried on effectually. 



Those near relations of the sharks and dog-fish, by the 

 way, the skates, lay eggs recalling those of the dog-fish, 

 but that the tendrils are short, projecting from the case 

 like four short handles, one at each corner of the oblong 

 case. In all the instances of egg-cases among the shark 

 tribe the walls of the egg are formed by two separate 

 plates, just as a walnut-shell is composed of two separate 

 valves. And these, in the case of the fish now under 

 discussion, just at hatching-time undergo a kind of de- 

 generation, so that the right and left halves of the upper 

 end split open and thus afford egress for the young. 



The eggs of all other fishes stand in strong contrast 

 with those of the shark tribe and chimaeras, in that they 

 have no shell. But some have remarkable modifications 

 of the outer sheath, as for instance in the case of the egg 

 of the smelt. As soon as this is laid the outer sheath 

 splits along the equator of the egg, and rapidly peels 

 ofiE, and turns inside out, remaining attached only at one 

 small circular area. The separated membrane now forms 

 a sort of adhesive swab, attaching itself to the piles of 

 bridges, posts, and other upright objects in the water, 



