ANATOMY OF THE CESTODES 193 



It was known long ago that the myoblasts adhere to the 

 dorso-ventral fibres as protuberant formations ; but it is only recently 

 that they have been found to be also muscle fibres in the form of large 

 star-shaped cells, which are not close to the fibres (fig. 118), but are 

 connected with them by offshoots (Blochmann, Zernecke). 



Within the scolex the direction and course of the muscular 

 layers change. 



The SUCKERS are farts of the musculature, locally trans- 

 formed, with a powerful development of the dorso-ventral muscles 

 into radial fibres. The ROSTELLUM of the armed tseniae, .like the 

 rostrum of the Rhynchobothridiae, also belongs to the same category 

 of organs. 



In the simplest form, the rostellum (as in Dipylidium caninum 



A m. 



FIG. 120. Rostellum of Dipy- FIG. 121. Head of Dipylidium 



lidium caninum. Lm., longi- caninum of the dog, with projected 



tudinal muscles; Am., annular rostellum. 71/1. Am., annular mus- 



muscles. cles ; Sp., suckers. 



=Tcenia cucumerina) appears as a closed oval sac, the anterior 

 part of which, projecting beyond the upper surface of the head, 

 carries several rows of hooks (figs. 120 and 121). The entire 

 internal space of the sac is occupied by an elastic, slightly fibrous 

 mass, while the anterior half of the surface of the rostellum is 

 covered by longitudinal fibres and the posterior half by annular 

 fibres. On contraction of the latter the entire mass is driven for- 

 wards, the surface of the rostellum becomes more arched, and the 

 position of the hooks is, in consequence, altered. The rostellum of 

 the large-hooked taeniae, wjiich inhabit the intestine of man and 

 beasts of prey, is of a far more complicated structure, for, in 

 addition to the somewhat LENTIFQRM rostellum carrying the hooks 

 on its outer surface, there are secondary muscles grouped in a cup- 

 13 



