HOW THE MAMMALS DEVELOPED 2OI 



these can attain maturity by the time the parents have 

 died, for the number of toads does not materially 

 alter season by season. The connecting string is made 

 up not of nourishment for the eggs, but of a bitter 

 mucous so unpleasant to the taste that fish are thus 

 deterred from eating the otherwise nourishing ma- 

 terial. This secures for the young embryo a chance 

 to mature which in the absence of the jelly it would 

 entirely lack. Imbedded in this mucous is the embryo 

 itself, surrounded by a small amount of albumen and 

 containing inside of itself a very considerable amount 

 of yolk. This gives to the egg a volume possibly a 

 hundred times that of the egg of the sunfish. Thus, 

 even counting the care the parent sunfish took of its 

 offspring, which care is very uncommon among fishes, 

 the toad stands a distinctly better chance in life. The 

 protection of the bitter mucous and the large amount 

 of yolk permitting considerably larger development 

 before leaving the egg, give to the toad a ma- 

 terial advantage. When the toad first emerges from 

 the egg it is amazingly like the fish. It has gills at 

 the side of its neck and swims by the movement of 

 its tail. Later its limbs develop, the hind ones coming 

 first, its tail is absorbed, and it is now a true toad, 

 ready to leave the water. 



Altogether a higher state of reproduction is en- 

 countered when we reach the reptiles, which are the 



