962 EEPORT OF COMMISSIONER OP FISH AND FISHERIES. [84] 



EXPLANATION OP PLATE XIX. 

 Fig. 17.— Telmatobrilus Vejdovskyi. 



Fig. 17 a. — A part of tho copulative organ of a young individual. The oviduct (■= ovdJ 

 is not yet fully differentiated, but is seen entirely inclosing peni 

 atrium, and prostata glands. 



17 h. — The same as above, in a fully developed individual. 



Fig. 18. — Limnodrilus alpestris. 



All the figures represent the copulative organs, demonstrating their mode of d^ 



velopment from the original generative gland to the fully developed form i 



the adult individual. 



Fig. 18 a. — The generative gland as it is first seen on the body wall of the tenth setig 



erous segment, seen from above. 



18 &. — The same as above, side view, and somewhat more magnified. 

 18 c. — The same gland, but in a more advanced state of development. The coi 



tical layer is well separated from the interior matrix. In the latter i| 

 seen the lumen of the penis. (This figure is from L. coralUnus.) 



18 d. — The same as above, in a yet more advanced state of development. In the 

 interior of the matrix is seen a semi-elliptic line (x x) separating the 

 future penis (p.) from the oviduct proper (ovd.). At x is seen the first 

 sign of the aperture of the penis sheath. (This figure is from L. aZpes- 

 tris.) 



18 /. — The first beginning of the efferent funnel. The aperture is not yet differ- 

 entiated. 



18 g. — The same as 18 d, but in a more advanced stage of development. The 

 cavity (ca.) between the oviduct and penis sheath is further developed, 

 but the oviduct (ovd.) is not yet fully separated from the penis and pe- 

 nis sheath, the connection being at c. The cavity between the penis 

 and the penis sheath is enlarging. The cortical layer (or.) forms an 

 exterior oviduct and is separated by a cavity from the interior sheath 

 of the oviduct (ovd.). 



18 h. — The same as above, in a more advanced stage of development. The interior 

 oviduct is fully separated from the penis sheath (p. ».), and the aper- 

 ture (in. ap. ) is defined. The penis sheath (jp. s. ) is also nearly fully sep- 

 arated from the penis, but connects as yet at x. The oviduct {ovd. ) and 

 the cortical layer are fully separated, but the former is yet connected 

 with the sexual porus. The aperture of the penis sheath is well de- 

 fined (ap. p. s.). 



18 k. — The lower end of a perfectly developed coijulative organ of a Limnodrilus, 

 with a single oviduct. The penis sheath is fully separated from the 

 penis proper. 



