86 Transactions of the Royal Canadian Institute, [vol. x. 



the cuticula, beyond the basement-membrane of which they could not be 

 traced. The space between the latter and the circular cuticular muscles 

 stains less deeply, since there seems to be a condensation of protoplasm 

 into strands which traverse it. In some places, in sections of young 

 strobilas, these processes appeared to be more or less grouped opposite 

 the columnar condensations in the syncitium, mentioned above. The 

 subcuticula is poorly developed in the scolex. 



Parenchyma. 



The parenchyma is divisible into the usual parts, a medulla ("Mark- 

 schicht"), at the centre of the strobila, surrounded by a cortex (" Rinden- 

 schicht"), extending to the subcuticula, the two being separated by the 

 longitudinal muscles. This division into two parts is based rather on the 

 arrangement of the nuclei, since the cytoplasm forms a very open 

 reticulum, excepting immediately around the nuclei (Fig. 35), in which 

 cell-boundaries cannot be seen. In the anterior proglottides most of 

 the nuclei, each from 4 to 5/i in diameter, are restricted to two regions, 

 those of the medulla close around the excretory vessels and nerve 

 strands, those of the cortex, much more numerous than the inner lot, 

 close to the subcuticula and among the outer transverse muscles. The 

 myoblastic nuclei of the transverse (inner especially) and dorso-ventral 

 muscles are easily confused at first sight with the nuclei of the 

 parenchyma, but on closer examination they are found to be somewhat 

 smaller and to contain more chromatin granules, a distinct nucleolus 

 being difficult to locate. The nuclei of the parenchyma, on the other 

 hand, are slightly smaller than those of the subcuticula. In Fig. 7 

 the two smallest nuclei farthest from the cuticle doubtless belong to 

 the peripheral region of the cortex. 



In young strobilas the parenchymatous reticulum is very vacuolated, 

 being indicated mostly by granules at the intersections of fine proto- 

 plasmic strands, while in mature proglottides it is evidently used up for 

 the growth of the reproductive organs which fill up almost the whole 

 space within the subcuticula. 



At the summit of the terminal disc of the scolex very many nuclei 

 are crowded around the small shallow depression to be found there in 

 many specimens, but they show no evidence of having any special func- 

 tion. Probably they have been pushed out of the immediate neighbour- 

 hood by the growth of the powerful muscles situated there (v.i.). 



In all of the material studied there appeared to be no traces of chalk 

 bodies in the parenchyma, not even spaces such as can be seen in plero- 

 cercoids of the genus Proteocephalus, which might have accom- 

 modated them before they were dissolved out by the acetic acid in the 

 fixing fluid. 



