Two New Trematodes of the Family Gyroclactylidae. g 



two smaller vessels, one proceeding forwards, the other backwards. 

 The posterior vessel winds along the internal border of the 

 intestinal ccecum on to the caudal portion of the body into the 

 region of the caudal glands, where it turns forwards and closely 

 follows its former course. The anterior vessel proceeds to the 

 region of the brain, where it is resolved into finer vessels. 

 Branches are given ont from various parts of the main vessel, 

 and the main vessels of the two sides of the body are connected 

 by a short commissure at their posterior ends, where they turn 

 upon their former course. In cross sections of the body the main 

 vessels are seen to run for the most part on the dorsal side of the 

 ventral nerves. 



The single testis is a large, dorsoventrally flattened, irregu- 

 larly globular organ situated between the intestinal cœca at the 

 middle of the body, and consisting of sperm mother cells and 

 spermatozoa in all stages of development, surrounded by a dense 

 layer of connective tissue. From its anterior end starts in the 

 median line a single vas deferens, which proceeds forwards and 

 obliquely to the left and in close contact with the ovary; at about 

 the anterior end of the latter it comes to lie between the 

 vitellarium and the left intestinal ccecum, which it embraces on 

 the outer side and then comes to lie on its ventral side between it 

 and the vitellarium, still continuing its forward course; then it 

 again turns towards the dorsal side and slightly backwards and 

 after forming an expanded ejaculatory duct richly provided with 

 circular muscle fibres, suddenly turns forwards again and opens at 

 the base of the chitinous penis (fig. 1, '2, 6). The latter is a hollow 

 tube with a lightly sigmoidal curvature and with a funnel-shaped 

 expansion at the base and an acorn-shaped one at the distal end, 

 the whole enclosed in a deep invagination of the genital atrium, 

 from which it can be protruded by the protractor muscles, which 

 are apparently specialisations of the dorsoventral fibres of the 

 body and consist of two bundles arising from the ventral cuticle 

 and attached to the expanded base of the penis. A rather strong 

 retractor muscle arises from the dorsal cuticle and is attached to 

 near the base of the penis opposite to the protractor muscles. 



