STRUCTURE OF THE SUBCUTICULAR LAYER. 289 



or lappet-like prolongations of the side-walls of T. perfoliata. Hence 

 the transverse muscles are but slightly developed at these points, and I 

 feel almost inclined to suppose that there is some connection between 

 them and the spindle-shaped cells, especially since the latter have, as 

 has been mentioned, been seen in direct connection with the former. 

 When one further notes that the direction of the spindle-cells in the 

 long-jointed Tcenice (Tcenia saginata, &c.) varies at the ends of the 

 proglottides in conformity with the muscle-fibres, one feels almost 

 warranted in regarding the spindle-shaped or subcuticular cells as a 

 sort of tendinous fibres. 



In agreement with this we may note that the spindle form of the 

 cells in question is but inconspicuous in the Bothriocephali (B. latus), 

 which have a poorly developed musculature. The filiform ends are 

 extremely delicate, and are very easily overlooked ; the cells them- 

 selves are closely grouped together in a thick layer. With the excep- 

 tion of the peculiar grouping, they exactly resemble the ordinary 

 connective-tissue cells of the rest of the parenchyma. 



If the above theory of the subcuticula be correct, then the Cestodes 

 have no epithelial membrane covering the body, and the same will 

 be true of the Trematodes. The cuticle cannot be genetically com- 

 pared with the cuticle of the lower animals ; it is rather the structure- 

 less limiting membrane of the connective-tissue substance, and is 

 comparable with the so-called basement membrane found in the other 

 flat-worms, and especially in the Planarians-, between the muscular 

 layer and the dermal epithelium. 



This is, indeed, a theory which has been formerly repeatedly main- 

 tained, particularly by Schneider, 1 and was suggested especially in 

 connection with the embryos of some species which throw off their 

 ciliated epithelium. Minot reports having seen, even in the adult 

 stages of Caryophyllceus, Tcenia, Botliriocephalus, &c., distinct cylindri- 

 cal cells on the uninjured cuticle. 2 This must, however, rest on a 

 confusion with the above described excreted layer. 



The histological and chemical nature of the Cestode cuticle can 

 hardly be used as an argument against regarding it as comparable 

 to the basilar membrane, for we know that in the lower animals 

 the connective substance occasionally assumes a thoroughly cuticular 

 character. 3 The only argument against this theory is the dogma 

 according to which the outer surface of every animal should during 



1 " Untersuchungen iiber Plathelminthen, " Vierzehnter Bericht d. oberhess. Gesellsch. 

 Natur- u. Heilkunde, p. 69, 1873. 



2 " Studien an Turbellarien " (loc. cii.), p. 456. 



3 I may refer to my observations on the intermuscular connective substance of the 

 Nematoda and Acanthocephali : see Vol. II. 



T 



