280 THE ANATOMY OF CESTODES. 



In our general discussion of the flat-worms we have already noted 

 that the Cestodes are parenchymatous animals. The whole body is 

 one mass, the continuity of the tissues is not broken by any visceral 

 cavity. The vegetative organs are embedded in the general substance 

 just like muscles or nerves. 



The simplest and most convincing proof of this is furnished by 

 their longitudinal and transverse sections, which are easily cut from 

 carefully hardened specimens, and which, with the help of the now 

 familiar staining and clarifying reagents, show the structure of the 

 organism most beautifully. ^ 



The Body-Parenchyma. — The mass of the Cestode body is in its 

 morphological and histological relations a hyaline connective tissue 

 of varying firmness, and developed so abundantly that one can almost 

 fancy that the whole body of the animal has been modelled out of it. 

 Externally, it is surrounded by a cuticle which is elevated at many 

 points, especially on the head, into little spikes and hooks. The in- 

 terior of the body, apart from the viscera, is traversed by muscular 

 fibres, which run sometimes singly, sometimes in bundles, and 

 generally in all three dimensions of space, so that the body-mass 

 can be contracted on all sides. The more conspicuous are the 

 longitudinal and transverse fibres, which at some distance from the 

 exterior are developed in such numbers, and so close to one another, 

 that the whole body-parenchyma is thus divided into two successive 

 outer and inner sheaths, which (following Eschricht) we will respec- 

 tively designate as "cortical layer" and "middle layer." ^ 



The middle layer is seen on cross section to be bounded externally 

 by a narrow clear border ^ (the strong muscular bands), and includes 

 the generative organs, the longitudinal vessels, and the nerve cords ; 

 while the cortical layer mainly consists of the numerous muscular 

 fibres, and a considerable number of round, solid, laminated concre- 

 tions — the so-called "calcareous bodies " — which contain a considerable 

 but varying proportion of lime salts. 



^ I need hardly mention that such methods were but Uttle known or practised when 

 the first edition of this work appeared (1862). So far as I know, I was the first to 

 apply them to the investigation of Helminths, or indeed of Invertebrata in general. I 

 mention this not to claim credit for it, but as an excuse for the errors which crept into 

 my former account, largely in consequence of my necessarily imperfect methods. 



' The latter includes the "transparent" layer distinguished by Eschricht in 5oiAno- 

 cephalus latus, and also the so-called ventral and dorsal granular layers. See Nova Acta 

 Acad. Cces. Leop.-Caroh, t. xi.x., Suppl. 2, 1841. 



" Pagenstecher believes (Zeitschr. f. wise, Zool., Ed. xxx., p. 177, 1878) that he can dis- 

 tinguish a narrow space within the muscular layers of Tamia critica. This he would repre- 

 sent as a body-cavity. I have never seen any such appearance in my examination of 

 numerous species. 



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