MOEPHOLOaiCAL PEDIGREES. 3 



essentially on the individuality of the observer. Zoologists 

 have hitherto been equally little able to avail themselves of any 

 aids to experiment analogous to those which are abundantly 

 open to the chemist and the physicist, to the physiologist 

 and even to the botanist. In this respect, indeed, zoologists 

 are very badly off — worse off than any other class of scientific 

 enquirers — for until lately they were simply directed to inter- 

 pret the facts presented to them by nature, without being in a 

 position to formulate their own problems or to force nature by 

 any critical expariments to give a distinct answer to them. 

 Hence any pedigree selected by one or another naturalist, 

 and based on facts derived from animal morphology, could, and 

 can, only avail to represent those ideas as to the affinities of 

 animals which their author in each case conceives to be the only 

 accurate ones ; and hence it must necessarily contain a larger or 

 smaller infusion of subjective fancy and unquestionable error. 

 Thus it is not very surprising to learn that a warm dispute has 

 just broken out as to which group of Invertebrate animals is 

 to be regarded as the closest in affinity to the Vertebrate ; 

 nor that the view, hardly of ten years' standing, that the 

 Vertebrata are allied to and derived from the Ascidians, is 

 combated, not without strong reason, by another — namely, 

 that they are more nearly allied to the Annelida — without either 

 side having hitherto proved itself victorious. Subjective views 

 inevitably play an important part in every scientific applica- 

 tion of the facts of animal morphology. 



We may, however, rest satisfied with these illustrations, and 

 proceed to the wider question, bow it was possible that nature 

 should have produced such an immense variety of forms as 

 is exhibited in the animal kingdom, without ever losing the 

 thread of affinity which the zoologist seeks to detect in animal 

 structures and to exhibit in his genealogies or systems. Darwin 

 has here supplied us with the . answer. He has shown, as it 

 seems to me in the most satisfactory and exhaustive manner, 

 that two properties inherent in organic beings have contributed, 

 in conjunction with other external natural factors, as means to 

 the accomplishment of this end : First, the power in the 

 parents of transmitting to their descendants their essential 



