TWO NEW SFECIKS OF ONYCHOPHORA. 521 



be equally possible." In tlie case of the egg of Paraperi- 

 patus, as well as in that of the Neotropical forms, he goes 

 even further and says, "There is no reason whatever to 

 suppose that there has been a secondary loss of yolk 

 in these cases" (18). He does not stop to argue and con- 

 sider the point, but gives us his conclusions unsupported by 

 either fact or argument of any kind. He begins the paragraph 

 from which the above quotations are taken as follows : — " I 

 will not attempt to discuss this very diflficult subject." 



Since Dr. Willey did not consider it advisable to make us 

 acquainted with the line of thought which led him to adopt 

 the above conclusions, he can hardly lind fault with us for 

 not accepting them, and perhaps for trying to supply the 

 reasons which induced him to adopt them. 



The view has been held for many years, and is being held 

 to-day — most probably quite correctly — that of all the forms 

 of PeripatidcO hitherto known, the Neotropical ones are 

 the most primitive. Kennel^ probably thinking that an 

 animal which is in several respects primitive must be so in 

 every respect, came to the conclusion that, since the 

 Neotropical forms are primitive as i-egards general cha- 

 racters, they must also possess a priniitive ovum; that is, as 

 he thought, a small yolkless ovum. Dr. Willey may have 

 unconsciously fallen into the same error, for he mentions 

 several features which he considers ])rimitive in Paraperi- 

 patus, for example, the structure of the male genital ducts, 

 and it is quite possible that for such reasons he has accepted 

 von Kennel's view of the original condition of the ovum in 

 the Peripatidte. 



Evidently there are two ways of explaining the structure 

 of the ovum of P. capensis. The condition of the ovum in 

 this species may be a vestigial one^ the yolk having been 

 lost, but the spaces in which the yolk was found in the not 

 very distant past, being still retained, as well as the com- 

 paratively large size of the ovum; oi- it may be a case of what 

 may be described as prophetic adaptation in phylogeuy, 

 the egg preparing itself — so to speak — for the reception of 



VOL. 44, PART 4. NEW SEKIKS. L L 



