October 3, 1913] 



SCIENCE 



459 



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 evolu- 

 tion versus creation we no longer wonder 

 that descendants slowly change and di- 

 verge. But we are rightly impressed when 

 unlike comes to produce like, since this 

 phenomenon seems to indicate a tendency, 

 a set purpose, a heau ideal, which line of 

 thought or rather imperfect way of expres- 

 sion leads dangerously near to the crassest 

 teleology. 



But, teleology apart, we can postulate a 

 perfect agreement in function and struc- 

 ture between creatures which have no com- 

 munity of descent. The notion that such 

 agreement must be due to blood-relation- 

 ship involved, among other difficulties, the 

 dangerous conclusion that the hypothetical 

 ancestor of a given genuine group possessed 

 in potentiality the Anlagen of all the char- 

 acters 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 ata- 

 vistic, a procedure which would turn the 

 revered ancestor of our species into a per- 

 fect 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 in- 

 stance, a remarkable resemblance between 

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

 Pythonomorph plioplatycarpus. If you 



homologize the mammalian tympanic with 

 the quadrate the resemblance loses much of 

 its perplexity, and certain Chelonians make 

 it easier to understand how the modifica- 

 tion may have been brought about. But, 

 although we can arrange the Chelonian, 

 Pythonomorph and Cetacean conditions in 

 a progressive line, this need not repre- 

 sent 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 homog- 

 eny of these bullm is excluded. In either 

 ease we stand before the problem of the 

 formation of a bulla as such. The signifi- 

 cant point is this, that although we dismiss 

 the bulla of whale and reptile as obvious, 

 homoplasy, such resemblances, if they oc- 

 cur in two orders of reptiles, we take as 

 indicative of relationship until positive evi- 

 dence 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 

 zoologists look upon such cases as a nuis- 

 ance and the underlying principle as a 

 bugbear. So far from that being the case 

 such study promises much beyond the pru- 

 ning of our standard trees — by relieving 

 them of what reveal themselves as grafts 

 instead of genuine growth — namely, the 

 revelation of one or other of the many 

 agencies in their growth and structure. 



Since there are all sorts and conditions 

 of resemblances we require technical terms. 

 Of these there is abundance, and it is with 

 reluctance that I propose adding to them. 

 I do so because unfortunately some terms 

 are undefined, perhaps not definable; 

 others have not ' ' caught on, ' ' or they suffer 

 from that mischievous law of priority in 

 nomenclature. 



The terms concerning morphological 



