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 

 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 



