MAMMALIAN CESTODES. 551 



the type species of the genus, Dipylidiwin canimivi. An in- 

 spection of the figure will render a detailed description of the 

 pvoglottids of the present species vinnecessary ; it will be noticed 

 that their number is small, not moi-e than 28. In another 

 ■specimen I only found 22. In this example (or in one very like 

 it) the last nine segments became suddenly very much more 

 •elongate, and were three to four times as long as broad. In 

 transverse sections the body shows an elliptical form pointed at 

 the two ends laterally and nearly as deep as wide. 



The general structure of the body shows certain differences in 

 the less mature and more mature segments, which do not appear 

 to me to be altogether due to the greater tension in the latter. 

 The specimen which I selected foi" examination by means of 

 transverse sections was much like that of which I give an entire 

 view in text-fig. 85. But in the posterior segments, though 

 short, the sexual organs were well developed, and there were 

 ripe ova lying in cavities (of which a full description will 

 be given later). In these transverse sections the cuticle is 

 very thick and the layer of subcuticular cells very conspicuous 

 and deeply stained ; they have the usual flask-shaped form 

 and lie in a dense layer, being closely adpressed. Their thinner 

 outer ends are in contact with the cuticle above them. Upon 

 this layer follows a layer of lax tissue, and then a strong 

 longitudinal layer of muscular fibres, which are themselves 

 separated from the medulla by a thinner layer of transverse 

 muscular fibres. These fibres are associated together in bundles 

 of three or four fibres, which are very stout ; there appear to be 

 also a few fibres to the outside, which are not associated in 

 bundles but implanted singly. In longitudinal sections it is 

 rather easier to count the number of fibres which lie in a single 

 I'adial row of this longitudinal layer, and I find that there are not 

 inore than five or six. Here and there between the bundles are 

 parenchymal cells whose deep staining as contrasted with that 

 of the muscular fibres emphasizes their existence. In sagittal 

 sections the subcuticular layer is also obvious in the more anterior 

 proglottids. I have not been able to get any transverse sections 

 of the more elongated posterior proglottids (owing to the limita- 

 tion of my material) ; but in longitudinal (sagittal) sections I 

 could find no trace whatever of elongated flask-shaped subcuticular 

 cells. The general cortical parenchyma reaches absolutely up to 

 the (here) very thin cuticle. There are, I think, only two possible 

 explanations of this appearance of vanished subcuticular cells. 

 First, that they have altered their form owing to the pvilling 

 out of the segment, and have become broader and round like the 

 cells which secrete the calcareous bodies ; or secondly, that they 

 are really absent from this region of the body. It is clear from 

 the observations of Lonnberg that the subcuticula varies among 

 tapeworms. It is, for example, in Tetrarhynchus tetrahothrius * " 



* "Anatomische Studien iiber Skandinavische Cestoden," K. Svensk. Ak. Handl. 

 xxiv. 1891, pi. i. figs. 6, 11. 



