32 THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITANNIAE. 



in which the embryo lies, which fit into corresponding depressions of the uterine 

 wall. One such ridge was also figured by Sclater round the embryonic vesicle of 

 the species investigated by him (P. imthurni = demeraranus). P. edwardsii = trinida- 

 densis is without such a ridge (Kennel). It therefore appears that the various 

 Neotropical species offer considerable differences inter se, in their development. The 

 uterine wall of the Neotropical Peripatus appears to differ from anything that has 

 been described in the other subgenera in that the thick wall of the uterus includes 

 and is traversed by blood-spaces. These were described and figured by Kennel, and 

 again figured by Sclater. Therefore I do not understand the following statement 

 made by the latter author. He says " In the case of Peripatus imthurni (demeraranus 

 Sedgwick), there is certainly, as far as I have been able to observe, no plexus of 

 blood-vessels at all [in the uterine wall] : and Kennel, I think, makes no mention of 

 this matter." 



In this quotation the use of the word " blood-vessels " instead of " blood-spaces " 

 is unfortunate. Kennel was also unfortunate in his selection of terms when he 

 applied the term "placenta" to the mechanism by which the embryo acquires its 

 nutrition. 



Morphology of the Trophoblastic Vesicle of P. novae-britanniae. 



While discharging its nutritive function, the trophic organ at the same time 

 serves as a water-cushion for the protection of the embryo, like the amnion of 

 higher Vertebrates (cf. Haddon quoted by Hubrecht 9). Thus the trophic organ has 

 a double function, (1) that of nutrition and (2) that of protection of the embryo. 

 The function of nutrition is its primary function while that of protection is quite a 



Fig. 7. Outline sketch or transverse section through the mid-region of the embryo shown in plate hi, 



Fig. 35. 



t.c. trophic cavity, v.o. thickened patches of ectoderm from which the nerve-cords are delaminated. These 

 unite later to form the ventral organs. 



