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 ail 
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 
cuuenin  eVOlution. According to the geological 
man. 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- 
