UNSBGMENTBD UTERINE OVA. 19 



in life by a structureless fluid, for they contain in preserved 

 specimens nothing presenting any structure, excepting the 

 small number of globules and granules already mentioned. It 

 can hardly be doubted, when the large size of the egg is con- 

 sidered, that some not very remote ancestors of the Cape 

 species must have possessed an ovum, heavily charged with 

 food yolk. We may further conclude from what we know of 

 the relationship of the food yolk to the protoplasmic reticulum 

 in other eggs, that this yolk must have been contained in the 

 meshes of the reticulum, which now contain only fluid. This 

 view is strongly confirmed by the fact that in a species of 

 Peripatus, living at the present day and closely resembling 

 Capensis, viz. P. novae zealandiae, the ovum is considerably 

 larger than that of Capensis (1'5 x 1 mm.), and contains a 

 large amount of food yolk. Our knowledge of the structure 

 and early development of the ovum of this species is very 

 small. It has been described by Hutton (6) and Kennel (8), 

 and I have cursorily examined ova removed from hardened 

 specimens. But the latter were too ill preserved to enable me 

 to arrive at any satisfactory conclusions as to their structure 

 and early development. There can, however, be no doubt on 

 the following points : — (1) They are very large, (2) they have a 

 thick chitinous shell, and (3) they are very heavily charged 

 with food yolk. The shell of the Cape species, is as already 

 stated, a somewhat delicate, transparent, structureless, but 

 dense membrane ; and within it, and much more closely applied 

 to the ovum, there is a second, apparently similar, but more 

 delicate membrane. 



It is interesting to notice here the small size ('04 mm.) of 

 the ovum of the West Indian species as described by Kennel. 

 The eggs of these three species seem to form a perfect series in 

 regard to size^ and amount of yolk, and it would be extremely 

 interesting to compare their structure and the early stage of 



1 Greatest length of ovum of P. novse zealandiae, 1'5 mm.; of P. 

 capensis, "S— -6 mm.; of P. Balfouri, -i— '5 mm. ; of P. Edwardsii. 

 •Oi mm. All the known species of Peripatus are viviparous and bring forth 

 fully developed joung. 



