178 



ONYCHOPHORA. 



with the result that the embryo becomes elongate (Fig. 88). 

 Dorsally, it is attached by the umbilical cord, while the ventral 

 surface is free. The blunt end becomes the head, and the pointed 

 end the posterior extremity. The blastopore, which is probably 

 secondarily displaced, lies quite near the latter (Fig. 89 A, bl). 

 The space between the blastopore and the umbilical cord is much 

 longer than that between the latter and the anterior end, since, 

 starting from the blastopore, new cell-material is continually being 

 produced posteriorly. Two mesoderm-bands, divided up into the 

 primitive segments, are present as in P. capensis, but, in conse- 

 quence of the smaller size of the egg, the paired nature of the 

 germ-band is not so distinct, although it can be recognised here 

 also (Fig. 89). 



The mouth arises in a position corresponding to that in P. capensis, 

 but quite independent of the blastopore, the latter, as a small and 



shallow depression, 

 having come to lie 

 at an early stage at 

 the posterior end 

 (Fig. 89 A, bl). The 

 anus also is said by 

 v. Kennel to arise 

 independently of the 

 blastopore. It arises 

 in front of the latter 

 as a slit-like depres- 

 sion (Fig. 89 A, a). 



<*•-- 



Fig. S6. — Embryos of P. novae-zealandiae. A, ventral, and B, 

 lateral aspect (after L. Sheldon), a, anus ; at, antennae ; 

 ex, limbs ; m, mouth. 



If the accounts given 

 of P. capensis by Sedg- 

 wick prove correct, we 

 shall have to conclude 

 that, in P. Edwardsii 

 also, the oral and anal 

 apertures were originally connected with the blastopore, since the position of 

 the two apertures is similar to that in P. capensis. 



With regard to the position of the growing zone, P. Edwardsii, according to 

 v. Kennel, agrees entirely with P. cajiensis and P. novae-zealandiac ; for since 

 this zone proceeds from the blastopore, and the latter lies behind the anus 

 (Fig. 89 A), the undifferentiated cell-mass is also found behind it. 



The connection of the embryo with the mother must here again 

 be referred to. According to v. Kennel, the embryo is connected 

 with the mother by means of the umbilical cord, as well as by the 



