Wilder.] 406 [December^), 



and Wyman (55, 260,) who think that " additional evidence, especially 

 from embryology, is needed before definite conclusions can" be reached." 



Embryology ought to determine whether the forward transfer of the 

 ventrals to beneath or even in front of the pectorals, in some Mala- 

 copteri, is a real shifting or only an ideal one, and if the former, 

 how it is accomplished ; for evidently our second proposition will not 

 be accepted by the " realists" in anatomy so long as the "legs" are 

 in front of the " arms" with any vertebrate, unless a sufficient account 

 can be given of the matter, enabling us to adduce the somewhat simi- 

 lar displacement of the eye in the Pleuronectidoe 1 which, by the way, 

 could be made to serve in the elucidation of both problems, since 

 Traquair's researches are not so complete as might be wished. 



As to the third question, there seems to be no dispute that the 

 omozone and ischizone do, in some way correspond; but both 

 Wyman and Humphrey, who have most ably discussed it, will now 

 doubtless admit that no determination of the special homologies of the 

 constituent bones can be other than provisional until the development 

 of the ischizone has been elucidated as completely as that of the 

 omozone has by Parker; and even then, we must know whether these 

 bones are to be compared syntropically or antitropically; the impor- 

 tance of such determinations is obvious on account of the great num- 

 ber of muscles which arise from the two arches. 



We have now to inquire whether the foregoing considerations justify 

 our acceptance of the proposition that the armus and skelos are 

 respectively appendages of the cephalic and caudal regions of the 

 trunk ; it seems to me that they do justify us in accepting it provision- 

 ally, and until it is satisfactorily shown, first, that there are more than 

 two pairs of membra, actual or potential, and second, that no such 

 thing as antitropy exists in the body itself. Till then, I think we are 

 entitled to study the membra as if they might be proved to be antitrop- 

 ically related, and to regard our success in such comparison as pre- 

 sumptive evidence of the correctness of our method. 



MEMBEAL OSTEOGENESIS. 



If, as is held by Darwin and others, the morphical value of a char- 

 acter is inversely to its apparent telical importance, I think a very 



1 Prof. Dana has in a letter to me stated that he now regards the relation of the 

 arms to the head as a functional one, not a structural, as admitted in 217, 341 ; and I 

 here beg to withdraw my own acceptance of what Parker calls the "peripatetic 

 morphology of the shoulder-girdle." 



