362 Miscellaneous. 



taken as tlie subject of his dissections some large tropical species, 

 and he has verified the exactness of the results obtained in the Qor- 

 cUus suhbifurcus of Europe. 



"We may distinguish, with M. Schneider, in the skin of all the true 

 Nematodes, two layers — the one internal and ceUular, lying directly 

 on the muscles, called the subcutaneous layer, and the other external, 

 the cuticle, secreted by the first. The two layers occur in exactly 

 the same way among the Gordiacea ; but M. Meissner entirely mis- 

 understood their nature. He considered the subcutaneous layer as 

 being in direct relation with the muscular system, and gave it the 

 name of perimysium. As to the cuticle, it is formed of two laminse, 

 of which the innermost was regarded by M. Meissner as a fibrillar 

 corium, and the external as an epidermis of cellular nature. 



In immediate dependence upon the skin is the organ which M. 

 Meissner has described as a ventral nervous cord. M. Schneider was 

 afterwards better inspired in regarding this cord as the homologue of 

 the ventral line of the Nematodes. Nevertheless, in his monograph 

 of the Nematodes, he abandons this opinion and regards the cord in 

 question as an oesophagus deprived of all communication with the 

 intestine — that is to say, as the morphological equivalent of an oeso- 

 phagus, not fulfilling the functions generally supposed to belong to 

 that part. It does not, indeed, present any mouth in front, or any 

 communication with the intestine behind. This interpretation is 

 energetically opposed by M. Grenacher. This observer recurs to \\ie 

 first idea of M. Schneider, and regards the supposed nervous cord as 

 homologous with the ventral line of the Nematodes. He shows be- 

 sides, by means of a series of very convincing sections, that this organ 

 is reaUy an excrescence of the subcutaneous layer. A narrow fissure 

 of the muscular cylinder along the ventral line permits a lamina to 

 pass, which establishes the continuity of the tissue between the sub- 

 cutaneous layer and the ventral cord. 



The muscular system of the body of Gordius forms in the interior 

 of the subcutaneous layer a cylindrical layer, internipted only along 

 the ventral surface by the gap through which the ventral cord com- 

 municates with the subcutaneous layer. This cylinder is composed 

 of laminae, which M. Schneider compares with the fibrillae of the 

 other Nematoda. M. Grenacher, on the contrary, regards each la- 

 mina as a muscular cell, homologous with those of the Polymyaria. 

 These laminae, indeed, are not solid, but each constitutes a tube, 

 though, it is true, of very small cahbre. The calibre is directly com- 

 parable to the medullary mass of the muscles in the other Nematoda. 

 The author has not, however, succeeded in finding the nucleus of 

 these muscular cells. 



The tube formed by the difierent layers of the body-wall that we 

 have just described is filled with a cellular tissue, in which the other 

 organs are immersed. This tissue is designated by M. Grenacher the 

 perienteric connective substance. It is to it that M. Meissner, by a 

 curious interpretation, ascribed the function of an intestinal canal. 

 He assumed, in fact, that the mouth led directly into the cavity filled 

 by this tissue ; so that the genital organs would have been lodged in 



