THE FREE-LIVING FLATWORMS (TURBELLARIA) 



351 



70 (67) With atrial copulatory apparatus. 



Castrada hofmanni (M. Braun) 1885. 



Length 1.5 mm. Unpigmented. Colored green from zoochlo- 

 rellae in mesenchyma. Cylindrical. Anterior end rounded, pos- 

 terior end running out to a blunt point. Without eyes. Large 

 rhabdoids in tracts. Pharynx somewhat before the middle of 

 the body with genital pore shortly back of it. Testes are elon- 

 gated oval to pear-shaped. Yolk glands are deeply lobed. The 

 male copulatory organ and bursa copulatrix are entirely enclosed 

 by the muscular mantle of the atrium copulatorium. Rochester, 

 N. Y. 



FIG. 623. Castrada hofmanni. Cirrus, bursa copulatrix, and atrium 

 copulatorium. Diagram from preparations subjected to pressure: vs, 

 vesicula seminalis; ks, granular secretions; sp, spermatophore; rm, cir- 

 cular muscles; t, teeth-like spines; ac, atrium copulatorium; de, ductus 

 ejaculatorius. Much enlarged. (After Luther.) 



71 (64) Testes dorsal or lateral to the yolk glands. Mesenchyma with 



rhabdoids outside of tracts. . Tribe MESOSTOMATINI . . 72 



Sexual pore lies in anterior two- thirds of body. Protonephridial ducts open through mouth 

 to exterior as in most Typhloplanini and in some cases, mouth, protonephridia, and genital 

 organs have a common external opening. Rhabdites play a very important part in classi- 

 fication. The larger rhabdocoels belong to this group. 



72 (73) With a -ventral epidermal pouch and a ductus spermaticus which 



connects the bursa copulatrix with the female genital canal. 



Bothromesostoma. 

 Only one species known in this country. 



Bothromesostoma personatum (O. Schmidt) 1848. 



Length 7 mm. Color on anterior and posterior ends and on lateral margins and ventral 

 side a clear brown. In mature specimens the pigment is so massed that together with the dark 

 color of the intestine it gives a dark brown to bluish-black color to the dorsal surface above the 

 intestine. Some specimens show a mixture of brown and black. The oval eyes are about as 

 far distant from the lateral margins as from each other. They are perceptible only in the 

 lighter pigmented specimens. The ventral epidermal pouch occurs somewhat- posterior to 

 the eyes. The common opening for mouth, protonephridial ducts, and genital pore is located 

 about the middle of the ventral surface. Both summer and winter eggs are produced. The 

 former produce the viviparous young. Ann Arbor, Mich. 



be 



FIG. 624. Bothromesostoma personatum. (A) entire animal. X 5. (After Schmidt.) (B) Diagram of 

 sexual organs: be, bursa copulatrix; dsp, ductus spermaticus; pm, opening of cirrus; rs, receptaculum 

 seminis; pg, genital pore; dg, duct of yolk gland; ph, pharynx; no, opening of protonephridium. Much 

 enlarged. (After Luther.) 



