122 F. H. STEWART. 



of 180°. The entire system lies ventral to the alimentary 

 canaL 



Each testicular region with its contents forms an elongated 

 mass, tapei-ing at either extremity. In cross sections the 

 outline varies from semicircular to triangular in adaptation 

 to the other internal organs. The anterior mass is the larger; 

 where it attains its greatest breadth it occupies as much as 

 two thirds of the body cavity. 



In preparations of the entire animal the richly cellular 

 character of the testis and the mass of developing sperms can 

 be readily distinguished. 



On examination by serial sections, the testicular region is 

 found to consist of a tube with epithelial walls, the commence- 

 ment occupied and closed by the germinal syncytium, the ter- 

 mination becoming continuous with the epithelial lining of the 

 ductus. 



The epithelium of the wall is, throughout the greater part 

 of the length, very fine and flattened (PI. 7, fig. 17, gw.). 

 It is only possible to demonstrate the protoplasm in places 

 where the contained sperms have been artificially separated, 

 but the flattened nuclei (ib., ngic.) are always readily de- 

 tected. Toward the junction with the ductus the epithelium 

 increases in depth, forming a well-marked layer still without 

 cell limits, but with fairly large oval nuclei. A fine layer of 

 muscular fibre appears on the outside. This portion is analo- 

 gous or, possibly, homologous with the vas deferens described 

 by Jiigerskiold (10) in Cylicolaimus magnus and Thora- 

 costoma acuticaudatum. 



The germinal syncytium (PI. 7, fig. 16) which occupies 

 the fundus consists of a mass of nucleated protoplasm, which 

 is in continuity with the protoplasm of the wall : in other 

 words, it is a specialised portion of the epithelium lining the 

 gonococl. From this syncytium the sperm mother-cells are 

 developed, growing down and filling the lumen of the tube, 

 multiplying and undergoing development as they pass down. 

 The nuclei of the syncytium at the commencement are 

 spherical, or oval, "0043 mm. in greatest diameter, have clearly 



