150 T. B. KOSSETER ON HYMENOLEPIS UPSILON, 



Chalk Corpuscles. Excepting in the vicinit}'- of the base of the 

 suckers, and here they are very sparingly distributed, there are 

 none in the strobila. 



The nervous system could not with any definite certainty be 

 traced. 



Muscular System. There are apparently sixteen longitudinal 

 muscles, eight ventral, and the same number dorsal. They 

 are arranged equidistant, and are composed of a number of 

 smaller muscle fibres which in the genital segments dissociate 

 themselves. These bundles are 3/x, in diameter. There is also 

 a series of smaller muscles running longitudinally through 

 the parenchyma of the strobila, ofi*shoots from which spread 

 themselves transversely, proximally and distally over the tissue, 

 and thus form a plexus in the segment. This is shown in the 

 ends of detached or teased-out segments. When the rostellum is 

 everted and the hooks sunk in the scolex, there is still a portion 

 of the rostellum extruded, and from the crateriform inversion 

 can be traced four protractor muscles running downwards, and 

 attaching themselves to the proximal circular periphery of the 

 bulb. The bulb is composed of a series of dense muscular ridges, 

 in the grooves of which are seated and attached the ten sickle- 

 shaped hooks. When fully extruded, as in Fig. 3a, four retractor 

 muscles possibly but a continuation of the protractors, as they 

 are attached at the same point on the periphery of the bulb run 

 longitudinally to the pyriform base, where they bifurcate and 

 attach themselves to the sides of the concavity. These retractors 

 are attached individually to circular muscle bands. Fig. 3/;, 

 running the whole length of the attenuated rostellum, as in the 

 rostellum of H. gracilis ; their commissures are somewhat 

 swollen. From the exterior or convex portion of the pyriform 

 body of the rostellum is given off in a radiate manner numerous 

 minute muscle fibres which imbed themselves in the surrounding 

 tissue of the scolex. 



Excretory System. The ventral and dorsal canals lie longi- 

 tudinally nearly in the same plane and are 0'027 mm. from either 

 lateral border, and their transverse canals are on the extreme 

 posterior margin of the segment. The former has a diameter of 

 14/x, and the latter 6/x. 



