BRITISH ASSOCIATION : ZOOLOGICAL SECTION. 359 



logical continuity. And yet how moderately is function dealt with 

 in his monumental text-book and how little is there in others, even 

 in text-books of Zoology ! 



Habt alle die Theile in der Hand, 



Fehlt leider nur das geistige Band — Life ! 



We have become accustomed to the fact that like begets like with 

 small differences, and from the accepted standpoint of evolution 

 versus creation we no longer wonder that descendants slowly change 

 and diverge. But we are rightly impressed when unlike comes to 

 produce like, since this phenomenon seems to indicate a tendency, a 

 set purpose, a beau ideal, which line of thought or rather imperfect 

 way of expression leads dangerously near to the crassest teleology. 



But, teleology apart, we can postulate a perfect agreement in 

 function and structure between creatures which have no community 

 of descent. The notion that such agreement must be due to blood- 

 relationship involved, among other difficulties, the dangerous con- 

 clusion that the hypothetical ancestor of a given genuine group 

 possessed in potentiality the Anlagen of all the characters exhibited 

 by one or other of the component members of the said group. 



The same line of thought explained the majority of human 

 abnormalities as atavistic, a procedure which would turn the revered 

 ancestor of our species into a perfect museum of antiquities, stocked 

 with tools for every possible emergency. 



The more elaborate certain resemblances are the more they seem 

 to bear the hall-mark of near affinity of their owners. When 

 occurring in far-related groups they are taken at least as indications 

 of the homology of the organs. There is, for instance, a remarkable 

 resemblance between the bulla of the whale's ear and that of the 

 Pythonomorph Plioplaty carpus. If you homologise the mammalian 

 tympanic with the quadrate the resemblance loses much of its 

 perplexity, and certain Chelonians make it easier to understand how 

 the modification may have been brought about. But, although we 

 can arrange the Chelonian, Pythonomorph, and Cetacean conditions in 

 a progressive line, this need not represent the pedigree of this bulla. 

 Nor is it necessarily referable to the same Anlage. Lastly, if, as 

 many anatomists believe, the reptilian quadrate appears in the 

 mammals as the incus, then all homology and homogeny of these 

 bullce is excluded. In either case we stand before the problem of the 

 formation of a bulla as such. The significant point is this, that 

 although we dismiss the bulla of whale and reptile as obvious 

 homoplasy, such resemblances, if they occur in two orders of reptiles, 

 we take as indicative of relationship until positive evidence to the 

 contrary is produced. That this is an unsound method is brought 

 home to us by an ever-increasing number of cases which tend to 

 throw suspicion on many of our reconstructions. Not a few zoolo- 

 gists look upon such cases as a nuisance and the underlying principle 

 as a bugbear. So far from that being the case, such study promises 

 much beyond the pruning of our standard trees — by relieving them 

 of what reveal themselves as grafts instead of genuine growth — 



