HOW THE MAMMALS DEVELOPED 201 
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 
