DR M'INTOSH ON SOME POINTS IN THE STRUCTURE OF TUBIFEX. 



267 



Plate X. 



Figure 1. Perivisceral corpuscles from Tubifex rivulorum after extrusion into the water. x 210 



diam. 

 Figure 2. a, b, c, Various forms assumed by the parasitic larva from the perivisceral chamber of 



Tubifex. x 210 diam. 

 Figure 3. Granular glands from the wall of the digestive cavity in situ. x 350 diam. 

 Figure 4. Isolated gland-cells similarly magnified. 

 Figure 5. Posterior end of the Tubifex from the lakes, showing the junction of the dorsal and ventral 



blood-vessels ; a, cuticle ; b, chorion and muscular coats ; c, ending of dorsal blood-vessel ; 



c, last perivisceral ; d, perivisceral and other corpuscles. x about 50 diam. 

 Figure 6. Portion of Tubifex rivulorum at the reproductive season ; a, seminal receptacle in the tenth 



segment ; b, coils of ciliated duct (vas deferens) ; c, testicle ; d, atrium (?) with a double 



outline under pressure ; e, e, elongated vascular branches from the eleventh and other 



segments for the supply of the developed generative products. x 55 diam. 

 Figure 7. Vascular ramifications on the supero-lateral surface of the intestine ; a, dorsal blood-vessel ; b , 



septum. x 210 diam. 

 Figure S. A lateral view of the seventh segment after the addition of chloroform ; d, dorsal vessel ; v, 



ventral ; p, perivisceral. x 210 diam. 

 Figure 9. Anterior portion of the elongated form from the lakes, showing the circulating system ; a 



dorsal blood-vessel ; b, ventral ; c, enlarged pulsating cavities or " hearts "of the peri- 



viscerals in action ; d, forking of ventral vessel. 

 Figure 10. Tip of the copulating organ protruding through the sexual pore ; a, hooks. x 210 diam. 

 Figure 11. Larval parasite from the lobule of the testis. x 210 diam. 



Figure 12. The eleventh segment, showing the development of the ovaries; a, cellulo-granular con- 

 tents ; b, investing membrane ; c, perivisceral corpuscles ; d, granular glands of intestine, 

 x 210 diam. 

 Figure 13. Curious ovoid structure from the anterior part of the eleventh segment of a specimen with 



largely developed ovaries. x 210 diam. 



