TWO NKW SPECIES OF ONYCHOPHOKA. 523 



piimitive. If tlieie was no diificulty in accepting Kennel's 

 vieAv before Eoperipatus was discovered, there certainly 

 seems to be a difficulty now that this genus has to be con- 

 sidered, and that of such a nature as cannot very easily be 

 put aside. When the genera Peripatus and Peri- 

 patoides are compared fi'om this point of view, it seems 

 less difficult to adopt Kennel^s view, because in Peri- 

 patoides the young are born small in size, or are hatched 

 from ova outside the body; but when Peripatus and Eo- 

 peripatus are compared this reason no longer exists. In 

 both Peripatus and Eoperipatus the young measure from 

 22 to 27 nun. in length at birth, and are coloured much in 

 the same way as the adult. 



If Kennel's and Willey'sviow be correct, the ovum of Eo- 

 peripatus must have acquired its yolk since it took to 

 uterine development, and the condition of the ovum in the 

 genus Peripatus would in this case be primitive; but if 

 Sedgwick's view be the correct one, the structui*e of the 

 ovum in Eoperipatus has been inherited from an ancestor 

 which discharged a yolk-bcaring egg either in water or on 

 land, and the condition of the ovum in the genus Peripatus 

 would be a secondarily acquired one. 



The above seems to be a fairly clear statement of the facts 

 of the proljlem discussed, if Kennel's view be correct, it 

 seems that we have to consider the question, what advan 

 tage would it be to Eoperipatus, once it had taken to 

 nourishing its young in the uteri, to produce yolk in its egg 

 as well? It is difficult enough to explain the presence of 

 yolk in the egg of Eoperipatus on the supposition that it 

 lias been inherited from a former ancestor which discharged 

 a yolk-bearing egg; for we should expect to find the yolk 

 disappearing, as in the genus Peripatopsis, when uterine 

 development became habitual ; but wheti we are asked 

 why yolk was produced after the uterine method had become 

 the habitual mode of development, we find it impossible to 

 answer, simply because we cannot conceive of any advantage 

 that would accrue to the animal in the struggle for life from 



