360 T. B. ROSSETER ON THE ANATOMY OF DICRANOTJENIA CORONULA. 



a fine layer of transverse muscle fibre mingled with cellular tissue ; 

 3rd, an epithelial layer of spindle cells ; 4th, a layer of broad 

 bundles of longitudinal muscles, and lastly a wide band of ring 

 muscles, which run completely round the proglottis, thus forming 

 its endothelium ; and then follows the parenchymatous tissue of 

 the cavity in which the organs of generation are embedded. This 

 last layer of ring muscles thickens considerably at the boundary 

 or rim of the proglottis, its density causing it to appear as a dark 

 band. It has a thickness of O'OOl mm. 



The longitudinal muscles are broad smooth muscles, commencing 

 in the scolex, where, as I have said above, they anastomose 

 with the retractor muscles. Through the narrow neck and early 

 formed segments they aggregrate together as if forming a solid 

 circular band of muscle fibres ; but as the segments develop they 

 disintegrate, and spread themselves out laterally, both dorsally 

 and ventrally, on each proglottis ; and to a casual observer they 

 would give the impression that they run continuously through 

 the whole length of the strobila. This would be an erroneous 

 interpretation, and it is only in prepared sections, and by the 

 aid of a high power that an accurate diagnosis of their structural 

 composition, and mode of attaching each proglottis can be 

 demonstrated. The method of attachment so as to facilitate 

 the separation of the ripe or " uterine " proglottides from the 

 strobila is by the aid of " spindle-cells." Leuckart held this 

 view in connexion with the musculature of Tcenia saginata, and 

 although I am unacquainted, experimentally, with the anatomy 

 of T. saginata, yet I am in a position to say, having made it my 

 especial study, that this method of prolongation of the longitudinal 

 muscles by the aid of spindle cells in the mammalian tape-worms, 

 of which T. saginata is made the type, is equally the same 

 in this representative, viz., Dicranotcenia coronula, of the avian 

 tape-worms. From my prepared specimens of this tape-worm 

 I deduce the following conclusions : Two spindle-cells (Fig. 2 a) 

 separate themselves one on either side of the longitudinal muscle ; 

 these cells are thus outgrowths from the parent muscle. They 

 are bi-polar ; the anterior pole or thread being but an elongation 

 of the cell proper, remains attached to the muscle ; whilst, from 

 the posterior fine polar fibre, the continuing longitudinal muscle 

 is evolved. 



These longitudinal muscles, as also the retractor muscle fibres, 



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