286 THE ANATOMY OF CESTODES. 



as the result of a moulting. This opinion I still maintain, even more 

 firmly than ever, and believe that I can support it on indisputable 

 grounds. 



I base my arguments mainly upon the state of affairs in the 

 bladder-worms, where this outer fringe may be quite regularly ob- 

 served, but not on the absorptive, i.e., the outer surface of the bladder, 

 but in a situation where this is impossible — namely, in the canal-hke 

 interior space of the so-called head, which is merely the future head 

 of the tape- worm in its invaginated state. 



The cuticle which clothes this head is therefore turned inwards 

 towards the above-mentioned canal space, and is repeatedly thrown 

 off and changed as the head rapidly grows. The cast cuticles remain 

 lying in the interior of the space, and more or less fill it. They have 

 exactly the finely granular appearance and the loose texture of the 

 usual fringe, except that they usually hang together as a membrane, 

 and only rarely, and that imperfectly, fall into rods. The outer — that 

 is, the youngest of these layers — for two or three can sometimes be dis- 

 tinguished — is in more or less close connection with the cuticle, just 

 as is the fringe with the cuticle of the tape-worm. 



I attach no special weight to the fact that the latter often takes 

 the form of a border of more or less distinct rods. This certainly does 

 not occur so generally and constantly as we are led to infer from 

 the reports of Schiefferdecker and Steudener, who speak of nothing 

 but "little hairs," or "cilia." It is, indeed, occasioned by the 

 rupture which follows in consequence of the increase of surface in 

 the growing proglottides, by forces, therefore, which were not so 

 powerful in the inverted head of the bladder-worm, which was re- 

 stricted in its longitudinal extension. I need hardly notice further 

 that the presence of the pore-canals must be a factor in the process. 

 The liberation of the so-called " covering membrane " on the above- 

 mentioned epithelial cells is only possible because of the pore-canals 

 which penetrate it.^ 



When I finally note that the connection between the proto- 

 plasmic threads and the subcuticular tissue has never been seen by 

 any one, but only imagined for the sake of the theory, and seems 

 in the highest degree improbable when we consider the histological 

 structure of this tissue, then 1 think I have said enough to show how 

 untenable that theory is, which attempts fundamentally to alter our 

 conception of the nature of endosmotic nutrition. 



The cuticle is, on the whole, fiat and smooth, but is raised at 

 certain points into little hairs, prickles, and hooks, which vary ex- 

 tremely in form and size. 



1 Compare also simHar Qi0tiZSi£lib^\Mi£(Q&QM'^e tubules of Rainey or Miescher 

 (p. 201). 



