224 L. Agassiz on the Natural Relations between 



and at the same time, most aquatic in their habits, preserv- 

 ing in their adult state, characters of the young, and habits 

 of the lower types ; this playful disposition being universal, 

 even among the most ferocious of the cat tribe. I shall ab- 

 stain purposely from tracing these comparisons higher up 

 among Monkeys, and in the human families, from fear of al- 

 luding to exciting topics ; but leave it to the philosophic 

 observer to consider how far the idea of an aquatic Monkey 

 is compatible with the high position which these animals 

 hold in the class of Mammalia ; and how curious it is that 

 in the human family there are races which differ so much in 

 their natural dispositions, mode of life, habits, and adaptation 

 to higher civilization ; and how closely these natural disposi- 

 tions are connected with apparently insignificant peculiarities 

 of structure. 



Upon reviewing the facts mentioned above, and the infer- 

 ences derived from the facts, no impartial observer can in 

 future deny the importance of the study of the natural re- 

 lations between animals and the media in which they live ; 

 and the close connection which exists between them and the 

 gradation of their structure. But this being the case, it 

 must be a matter of surprise that the views so long enter- 

 tained of the importance of this connection, which led earlier 

 naturalists, generally, to the classification of animals accord- 

 ing to the media in which they live, vshould have been so 

 completely abandoned, and even considered of no value at all 

 in systematic classification. For my own part, I have no doubt 

 that this negative result has arisen from the circumstance 

 that also aquatic animals were brought together, in these 

 earlier attempts, without reference to their structure or or- 

 ganic development, while we have found that structure is the 

 ruling principle, and that natural connection with the element, 

 is the secondary motive by which these connections are in- 

 fluenced. Indeed, aquatic animals, though agreeing in many 

 respects, aad though provided with analogous apparatus to 

 perform the same functions, have, in different types of the ani- 

 mal kingdom, a very different plan of structure, and very dif- 

 ferent organs to perform the same functions. I shall not enter 

 into a detailed illustration of these differences, as I have al- 



