VOYAGE FROM NEW YORK TO RIO DE JANEIRO. 23 
admit that the gradation which unquestionably unites all 
animals is an intellectual, not a material one. It exists in 
the Mind which made them. As the works of a human 
intellect are bound together by mental kinship, so are the 
thoughts of the Creator spiritually united. I think that 
considerations like these should be an inducement for us all 
to collect the young of as many animals as possible on this 
journey. In so doing we may change the fundamental 
principles of classification, and confer a lasting benefit on 
science. 
" It is very important to select the right animals for such 
investigations. I can conceive that a lifetime should be 
O 
passed in embryological studies, and yet little be learned of 
the principles of classification. The embryology of the 
worm, for instance, would not give us the natural classifica- 
tion of the Articulates, because we should see only the first 
step of the series ; we should not reach the sequence of the 
development. It would be like reading over and over again 
the first chapter of a story. The embryology of the Insects, 
on the contrary, would give us the whole succession of a 
scale on the lowest level of which the Worms remain forever. 
So the embryology of the frog will give us the classification 
of the group to which it belongs, but the embryology of the 
Cecilia, the lowest order in the group, will give us only the 
initiatory steps. In the same way the naturalist who, in 
studying the embryology of the reptiles, should begin with 
their lowest representatives, the serpents, would make a 
great mistake. But take the alligator, so abundant in the 
regions to which we are going. An alligator's egg in the 
earliest condition of growth has never been opened by a 
naturalist. The young have been occasionally taken from 
the egg just before hatching, but absolutely nothing is known 
