40 FOOT-NOTES TO EVOLUTION. 



taining the frogs and salamanders, in which the eggs are 

 not large enough to serve the conditions of the problem. 

 So the matter was allowed to rest until new evidence 

 should be found. It came in 1864. In that year Pro- 

 fessor Cope found the remains of certain reptiles in the 

 rocks of Texas which he, not being aware of the em- 

 bryological problem, stated must be regarded as the 

 ancestors of both birds and mammals. His evidence 

 was solely derived from the bony structure. As all 

 reptiles have eggs in which there is a large amount of 

 food yolk, this discovery answered all the requirements 

 of the problem. Both embryology and geology were in 

 full accord. But the end was not yet. In the same 

 year, and a few weeks later, Caldwell and Haacke dis- 

 covered that two of the species of monotremes, those 

 wonderful bird-like mammals for which Australia is 

 noted — the duckbill and the spiny ant-eater — do not 

 nourish their embryos like other mammals, but that 

 they, like birds, lay eggs. It was found, further, that 

 these eggs are large; they contain a large amount of 

 food yolk, and they develop at first in the same way as 

 the eggs of reptiles. Here was additional confirmation 

 of the embryological conclusions. 



" There are many other features in the development 

 of the mammals which are equally wonderful and con- 

 clusive of the truth of the theory of 

 Embryonic , .• . j- , 1 , • 1 



' . evolution. Accordmg to the geological 



structures in o o & 



jnan record, man must be descended from 



mammals with tails. We find that in 

 the early stages of the embryo of man there is a time 

 when there exists a regular tail supported by eight dis- 

 tinct bones, like the tail bones of any other mammal. 

 With growth, however, these bones unite and all disap- 

 pear except three, which, joined in one, persist in the 

 adult. On the theory of evolution this tail is easily ex- 



