182 Scientific Intelligence — Zoology. 



bird, or a young snake, at a certain period of their growth within the 

 egg, resemble each other so much, that he would defy the most able 

 zoologl t of our day to distinguish between a robin and a bat, or 

 between a robin and a snake. There is something of high signifi- 

 cance in this fact. There is something common to all these. There 

 is a thought behind these material phenomena, which shews that 

 they are all combined under one rule, and that they only come under 

 dift'erent laws of development, to assume, finally, different shapes, 

 according to the object for which they were introduced. 



There is a period of life, in which, whatever may be the final form 

 of their organs of locomotion, whatever may be the final difference 

 between the anterior and posterior extremities, vertebrated animals 

 have uniform legs, in the shape of little paddles or fins. This is the 

 case with lizards as well as birds A robin's wing and a robin"'s leg, 

 which are so different from a bat's wing and a bat's leg, do not essen- 

 tially differ when young from the leg and arm of a bat. Wherever 

 we observe combined fingers preserving this condition, we have a 

 decided indication that such animals rank lower in the group to 

 which they belong. This is all-important, as we are enabled at once 

 to group animals which are otherwise allied, in a natural series, as 

 soon as we know whether they have combined or divided fingers. 

 And the degree of division to which the legs rise in their develop- 

 ment is a safe guide in our classification. Look, for instance, at the 

 legs of dogs and cats, in which the fingers are completely separated, 

 and so elongated, that the animals walk naturally upon tip-toe, and 

 compare them with others, bears, for instance, which walk upon the 

 whole sole of the foot ; and, again, with those of seals or bats, which 

 remain united, and constitute either fins or a wing. 



There are other reasons sufficient to convince us that the order 

 of arrangement which he had assigned them, according the develop- 

 ment of the fingers, is justified by the state of development of the 

 other organs of the mammalia, and especially of their higher organs 

 and intellectual faculties and instincts. And I will also add, says 

 Professor Agassiz, that mankind are not excluded from this connec- 

 tion, but, in common with other vertebrata, we are all at one stage 

 of existence provided with paddles or fins, which are afterwards de- 

 veloped into legs and arms. — AmeHcan Annual of Scientific Dis- 

 covery, p. 324. 



16. The Manatus or Sea Cow, the Embryonic Type of the 

 Pachydermata ? — Professor Agassiz thinks that the Manati have 

 been improperly considered cetaceans : they differ from them in the 

 form of the skull, which is elongated, and in the position of the 

 nostrils, which are in front. On the other hand, the skull resembles 

 that of the elephant in front (particularly when seen from above), in 

 some of the details of the facial bones, which are not like those of 

 the cetacea, in the palatine bones, the arrangement of the teeth, 

 and in the curve of the lower jaw-. Professor Agassiz, believed 



