86 Dr. C. Collingwood on Recurrent Animal Fornij 



tendency to assimilate with the habits naturally exhibited by 

 those animals whose form they assume. It is not easy to com- 

 pare the habits of animals essentially different in structure, and 

 occupying widely separated positions in the animal kingdom ; 

 but a few examples taken from within a Class will illustrate my 

 meaning, and give us an opportunity of carrying the arrange- 

 ment forward to cases of greater complexity. Thus, the Ursine 

 Opossum (Dasyurus ursinus), widely separated as it is from the 

 Plantigrade Carnivora, not only agrees far more closely with a 

 Bear in form than with its own congeners, having a short clumsy 

 figure and Plantigrade step, but it is said of them, by their 

 discoverers, that " they frequently sat on their hind parts, and 

 used their fore paws to convey food to their mouths, and many 

 of their actions, as well as their gait, strikingly resembled those 

 of a Bear .*." 



The Quadrumanous Douroucouli (Nyctipithecus felinus) not 

 only resembles a Cat in form, but is, like it, nocturnal in its 

 habits, glides about with the stealthy movements of a cat, and 

 " when irritated, in the posture it assumes, and the puffed state 

 of the fur, it resembles a cat attacked by a dog." The pachy- 

 dermatous Hyrax lives gregariously in burrows, like the Rab- 

 bits, which it so closely resembles in form. The Echidna rolls 

 itself up into a ball when disturbed, like its homomorph the 

 Hedgehog ; the Lemurine Galeopithecus makes its flight with its 

 young attached to the nipple, as do the true Bats. The habits 

 and food of the Sea Eagle closely agree with those of the Alba- 

 tros ; and the Burrowing Owl is diurnal in its habits, and uses 

 its feet more or less for purposes of scratching, in both which 

 respects it differs from its congeners, and agrees with the Ra- 

 sores, which it resembles in form. 



In all these cases — and the list might be greatly swelled — 

 the agreement between form and habit, independent of homo- 

 logical relations, is so striking that one is almost led to the 

 conclusion that a certain external configuration necessitated 

 certain habitual movements. I do not mean to say that this is 

 the case ; but I am inclined to think that a more careful review 

 will lead us to the conviction that the converse of this proposi- 

 tion is the secret, not only of these, but of the other striking 

 cases of homomorphism, as it has been called, to which reference 

 has already been made. 



The principle may be thus stated: — That agreement of habit 

 in widely -separated groups is accompanied by similarity of form. 

 Let us now see if we are not justified in deriving such a prin- 

 ciple from instances such as those just adduced, added to what 

 knowledge we possess with regard to the habits of animals in 

 * G. P. Harris, in Linn. Trans, ix. p. 174. 



