THE ANATOMY OF PENTASTOMUM TERETIUSCULUM. 41 



From the dorso-lateral parts of the ovary a continuous 

 '^crest^' of cells has grown out on each side, and into this, at 

 intervals which possibly (but of this I am not quite sure) cor- 

 respond with the annuli of the body, extend pouch-like diverti- 

 cula of the central cavity (fig. 44, L. S. 0.). The section 

 figured passes on one side through one of the latter. In the 

 central cavity is a coagulum, which may perhaps contain sper- 

 matozoa, though it is extremely difficult to definitely establish 

 the presence of these. 



The cells composing the "crest" on either side are distinct 

 in outline, and each contains a well-marked nucleus. The 

 dorsal mesentery {Mes.) is prominent, and composed mainly 

 of rounded cells, and is continuous with a somewhat flattened 

 layer of cells on the dorsal surface of the ovary. 



Leuckart described the cells which in P. tsenioides clearly 

 correspond to those of the " crest ^' above mentioned as being 

 enclosed in definite follicles. There is no appearance of any 

 such structures in P. t ere tiu senium, either now or at any 

 period, and the crest on each side is formed as a lateral growth 

 from the dorsal wall of the ovarian tube. This dorsal wall 

 may be regarded as a syncytium, the nuclei of which are con- 

 tinually dividing ; whilst in the lateral portions the protoplasm 

 becomes aggregated around them to form definite cells, which 

 by constant growth are, as it were, pushed over into the 

 " crest. '^ 



There is as yet no trace of any shell round the ova. In the 

 adult form the ovary occupies the same position as in the 

 young one, running immediately above the alimentary canal 

 from the posterior end to a point which lies a little behind the 

 anterior extremity of the mid-gut (fig. 7). It has the same 

 structure along its whole length (fig. 43). The ventral wall is 

 composed of a single layer of columnar cells, in which no 

 nuclei can now be distinguished, and many of which have the 

 appearance of glandular cells which have poured out their con- 

 tents, the remains of which are most likely represented by 

 small coagulated masses, which lie upon the internal ends of 

 the cells in the lumen of the tube. 



