The Theory of Evolution 41 
the anatomical evidence alone, that the progression had been 
in some such order as the geological record shows. The 
limitation referred to above is this: that while the mammals 
arose later than the birds, we need not suppose that the 
mammals arose from the birds, and not even: perhaps from 
the reptiles, or at least not from reptiles like those living 
at the present day. The mammals may in fact, as some 
anatomists believe, have come direct from amphibian-like 
forms. If this is the case, we find the amphibians giving rise 
on one hand to reptiles and these to birds, and on the other 
hand to mammals. 
This case illustrates how careful we should be in interpret- 
ing the record, since two or more separate branches or orders 
may arise independently from the same lower group. If the 
mammals arose from the amphibians later than did the rep- 
tiles, it would be easy to make the mistake, if the record was 
incomplete at this stage, of supposing that the mammals had 
come directly from the reptiles. 
That the birds arose as an offshoot from reptile-like forms 
is not only probable on anatomical grounds, but the geo- 
logical record has furnished us with forms like archzeop- 
teryx, which in many ways appears to stand midway between 
the reptiles and birds. This fossil, archeopteryx, has a bird- 
like form with feathered wings, and at the same time has a 
beak with reptilian teeth, and a long, feathered tail with a 
core of vertebre. 
From another point of view we see how difficult may be 
the interpretation of the geological record, when we recall 
that throughout the entire period of evolution of the verte- 
brates the fishes, amphibians, reptiles, and birds remained still 
in existence, although they, or some of them, may have at 
one time given origin to new forms. In fact, all these groups 
are alive and in a flourishing condition at the present time. 
The fact illustrates another point of importance, namely, that 
we must not infer that because a group gives rise to a higher 
