ON THE SEXUAL PHASE IN CERTAIN OE THE NAIPID^E. 793 



as the intestine, are profoundly affected ; the canal becomes impervious for long 

 distances and is represented merely by a narrow cord. In Haemonais the appearances 

 are similar, though not (in the specimens which I examined) quite so extreme. As 

 in the Polychseta above described, the atrophy cannot be caused merely by the 

 pressure of the genital products ; it occurs over a far more extensive region than 

 that occupied by the genital organs ; and (cf. figures of transverse sections of 

 Haemonais) no particular compression is exerted on the tube even in the genital 

 segments themselves. It would appear that the attainment of sexuality marks the 

 end of the individual's life, and that the material of the alimentary wall, being now 

 no longer of use, is in some way brought into solution and added to the reserves 

 of the ova. 



II. The Genital Organs in the Genus Slafina. (Plate LXXX.) 



The reproductive organs appear to be unknown as yet in any species of the 

 genus Slavina. 



The material from which the sexual individuals here described was obtained, 

 was taken in March 1914 from the duck-pond in the Zoological Gardens, Lahore. 

 The specimens belong to the species which I have described (Mem. Lid. Museum, 

 vol. i, No. 3, 1909) under the name of Slavina punjabensis* A semi-diagrammatic 

 illustration of the genital region is given in fig. 4. 



The clitellum is not very obvious ; it includes segments v, vi, and vii. 



The testes were not visible in the fully mature animal ; in a specimen which was 

 only in the earliest stage of the development of the reproductive organs, the testes 

 were seen as large masses in segment v, attached to the posterior face of septum 

 4/5 near the junction of the latter with the ventral body-wall ; each constitutes an 

 elongated mass stretching upwards and backwards. 



The sperm-sac, in the mature animal, is a diverticulum backwards from septum 

 5/6, with a wide anterior opening, which is partially closed by the male funnels. 

 The sac extends back through segments vii and viii, it may be as far as x ; it is 

 contained (behind the level of septum 6/7) within the ovisac. 



The male funnels are of fair size, and face backwards into the sperm-sac, the 

 opening of which they thus partially fill up. The vas deferens leads directly 

 downwards for some distance, supported by septum 5/6 ; then entering segment vi, 

 it shortly afterwards turns upwards, thus forming a loop with its convexity down- 

 wards ; the ascending limb of the loop is quite short, and the duct soon enters the 

 atrium on the anterior face, much below the middle point of the height of the latter. 

 The nuclei of the vas are oval, and transversely placed with regard to the axis of the 

 tube ; its diameter is 12-18 /*. 



The atrium is a large subspherical mass, taking up the whole length of segment 



* Miehaelsen ("Die Oligocliacten Columbias," Mem. Soc. Neuchdteloise des Sc. Nat., vol. v, 1913) thinks my form is 

 identical with S. appendiculata (Udek.). I am not yet convinced that this is so ; but the description here given will, 

 when the discovery of sexual individuals of S. appendiculata allows a comparison to be made, decide tbe matter. 



