vin ESSENTIAL AND ADAPTIVE CHARACTERS 119 



Another valuable guiding principle in morphological studies 

 is this. It is a remark of Gegenbaur's, in his valuable work 

 " On the Structure of the Carpus and Tarsus" but it must 

 have occurred to any one who has given much thought to 

 these problems. When we wish to discover the distinguishing 

 characters between different organisms, it is necessary to 

 examine them in their most fully developed condition. If, on 

 the other hand, our object is to trace their resemblance, their 

 intimate relationships, we must study them in their early 

 embryonic stages. By these methods we can do much to 

 separate what is secondary or superadded from what is funda- 

 mental or essential in the character of an animal. The 

 farther back we can carry our researches, the more prominent 

 do the characters, common to the whole group to which the 

 animal belongs, become. The more completely mature the 

 specimen, the more do the special characters of the species or 

 even of the individual predominate. 



It is not my province in these lectures to indulge much in 

 speculations. Indeed, as students of morphology, we are as 

 yet little in a position to do so. I shall not say much more 

 even on the general views to which I have lately referred, for 

 I feel that the acquisition of a sound basis of fact to work 

 with is what is, at present, most needed in comparative 

 anatomy. The difficulties which beset the beginner, and 

 indeed the more advanced student, in this subject are very 

 great. As regards, the branch to which I propose more par- 

 ticularly to direct your attention, the anatomy of the class 

 Mammalia, which, we might suppose, was better worked out 

 than any other, the information to be found in books is 

 scattered, fragmentary, unequal, and often untrustworthy ; 

 even good elementary treatises are wanting, much more 

 anything like an exhaustive work. Moreover, our museum 

 superior as I believe it to be to any other of the kind is, as 

 yet, far from adequate to supply the knowledge frequently 

 sought for in it. 



In considering the special subject for these lectures, I have 

 often thought that the greatest permanent benefit would be 

 conferred on our science by collecting together in a systematic 



