CHAPTER XXV. 



ONYCHOPHORA (Peripatus). 



Structure of the Eggs and Nourishment of the Young by the 

 Mother. The eggs of Peripatus pass through their development in 

 the uterus, but there is considerable variation in this respect in the 

 different geographical species. This point has been carefully investi- 

 gated up to the present time in P. novae-zealandiae (Australia), P. 

 capensis and P. Balfouri (Africa), and P. Edicardsii, torquatus, and 

 Imthurni (South America). These species differ even in the size of 

 the egg and of the mature embryo. The oval eggs of P. novae- 

 zecdandiae are 1*5 mm. long and 1 mm. broad, and the young which 

 hatch from them are not much larger than the eggs themselves ; the 

 eggs of P. capensis and P. Balfouri are 0*4-0*6 mm. long, but the 

 newly-hatched young of the former has a length of 10-15 mm., and 

 that of the latter is about half as long. In P. Edwardsii the mature 

 embryo attains the length of 22 mm., i.e., a third of that of the 

 mother, while the egg is here only 0*04 in diameter. The species 

 in which the young aie largest at birth have thus the smallest eggs,, 

 and vice versa. The explanation of this striking fact is to be found 

 in the circumstance that in the South American species the egg or 

 embryo remains in close connection with the mother, and is nourished 

 by means of a "placenta and an umbilical cord" (Fig. 88, p. 179).* 

 This accounts for the extraordinarily small size of the eggs in this 

 case, and for their being devoid of nutritive material. In the 

 African species the eggs are larger, but the newly-hatched young 

 are smaller than in P. Edwardsii, there being no correlation between 

 the size of the egg and that of the embryo, the latter, although not 



* We are here following the definite statements of v. Kennel (Xo. 4), which 

 rest upon his own observations, although we are aware of the statements made 

 by Hutton (No. 3) as to the size of the newly-hatched young of P. novae- 

 zealandiae. These, according to this latter author, measure from 8 to 10 mm. 

 Since v. Kennel's statements were not contradicted by the more recent 

 observers of the Peripatus of New Zealand, we must assume that the difference 

 is only apparent, and that the large size of the embryo as compared with that 

 of the egg must be traced not to its greater mass, but rather to its increase in 

 length and to its extension after leaving the egg. 



