STEUCTtJEE OP EARTHWOEM ALLIED TO NEMEETODEILUS. 567 



more diagrammatic ally in fig. 9 ; the latter figure shows the 

 relations of the sac to neighbouring organs. The sac is of a 

 brownish-yellow colour, and of an irregular elongated form; 

 it is marked here and there by furrows, which indicate that it 

 is capable of being extended to a much greater size ; it com- 

 pletely covers the dorsal vessel and oesophagus, to which it is 

 attached by a series of thread-like ligaments. The sac extends 

 when fully developed from the anterior boundary of Segment 

 13 to the posterior extremity of Segment 18 ; it gives off on 

 either side three diverticula ; from the first pair of those 

 diverticula arise the oviducts which pass outwards so far as 

 already stated upon the 15th segment. Anteriorly the sac 

 divides so as to embrace the oesophagus, round which it forms 

 a ring ; immediately beneath the oesophagus the two halves 

 become reunited, and pass forwards and downwards in close 

 contiguity to the septum separating Segments 12 and 13. In 

 this region the sac is very much narrower ; at the nerve-cord 

 the sac again divides so as to surround the cord, and the un- 

 paired duct which arises from this perineural ring opens on to 

 the exterior in the 13th segment. The sac was found to be 

 filled with bundles of spermatozoa of irregular shapes and 

 sizes ; a fragment of this sac taken from the living ovum and 

 teased up upon a slide showed that it was lined with peculiar 

 granular cells. The cells are so easily detached that it appeared 

 as if they were free in the interior of the sac ; an examination 

 of hardened material showed that this was not so, and that the 

 cells form a lining to the sac. The fresh cells are of an irre- 

 gular, generally somewhat elongated form; occasionally they 

 are branched ; the protoplasm of the cell is very clear and 

 transparent ; in the protoplasm are a quantity of spheroidal 

 granules, usually massed together in the widest part of the 

 cell ; the cells resemble very closely the peritoneal cells which 

 cover the alimentary tract, but the granules in their interior 

 are greyish instead of brownish green. 



In sections of the mature spermathecal sac (see fig. 12) 

 its walls are seen to be muscular, with a coating and lining of 

 epithelium. 



