92 Transactions of the Royal Canadian Institute. [vol. x. 



of fibres figured by Zograf ('92) for the scolex of Triaenophorus nodulosus 

 (Pall.) and observed by the writer in confirmatory sections. 



The sagittal fibres are arranged in the posterior portion of the scolex 

 in quite the same way as those of the foremost joints. As you follow them 

 forward, however, the two middle groups, that is, those between the 

 excretory vessels, which separate somewhat to accommodate them (Fig. 

 34), enlarge considerably to form the chief muscles of the bothria. Con- 

 traction of these in conjunction with that of the tangentially arranged 

 transverse fibres will deepen the bothria and thus form an efficient 

 sucking-apparatus. By their relaxation and the contraction of the cor- 

 onal fibres the bothria will, on the other hand, be loosened from the 

 substratum. Anteriorly the dorso-ventral fibres gradually diminish 

 in number and size until none appear in the first yOfi of the scolex from 

 the summit. 



The inner longitudinal muscles of the parenchyma do not pass to the 

 tip as in many Bothriocephalids, but only about half way along the 

 scolex, where they disappear. 



The outer longitudinal fibres are arranged as in the foremost joints, 

 but they are slightly more numerous. They extend forward as four 

 groups each of which is situated near poorly developed cuticular muscles 

 at the edge of the bothrial wall outside of the tangential groups (Fig. 34) 

 ahead of which they do not appear, that is, they do not pass to the tip 

 of the scolex. 



The second group of muscles peculiar to the scolex only is to be seen 

 in its anterior third. These are longitudinally arcuate fibres arranged 

 concentrically around the edges of the terminal disc in four groups, one 

 at each end of the diagonal diameters of the section through this region. 

 Their function is obviously to protract the edge of the former with its 

 bands of minute spines (Fig. 37). 



The individual fibres of the transversely and longitudinally arcuate 

 as well as those of the dorso-ventral bothrial muscles are comparatively 

 short and spindle-shaped. Approximately their middle thirds take the 

 strain much more readily (Figs. 34 and 37) than their ends which seem 

 more muscular in composition and can be easily followed to the cuticle. 

 This is due to the fact that it is in this middle portion that most of the 

 cytoplasm and the nucleus are located (Fig. loc). 



The musculature of the end-proglottis bears out the above statement 

 that an earlier portion of the strobila seems to be missing. The longitu- 

 dinal muscles of the parenchyma dwindle down rapidly, the individual 

 fibres diverging near the end-vesicle of the excretory system, while the 

 cuticular fibres, excepting a few circular ones which pass farther on 

 towards the latter, quickly disappear among the much altered subcuti- 

 cular cells on the hinder border of the terminal joint (Fig. 12). 



