304 ENTOZOA. 



possibly capable of being separated into several distinct lamellae, 

 like the cleavage layers of a mica sheet, and tlie circumstance that 

 the layer in question is not originally a distinct cell-membrane, but 

 a chitinous secretion from the primary integument, would favour 

 such a pecuharity. I can only account for Czermak's layers on 

 this supposition. On placing these worms in a solution of carmine, 

 I find all the true cell tissues become coloured, whilst the chitinoas 

 covering remains unaffected. As regards the inner or true integu- 

 mentary layer, this has been supposed to consist of fibres variously 

 blended, by which there have been recognized transverse longitudinal 

 and oblique lines. These linear groupings have generally been held 

 to constitute so many different layers, and certain of them have 

 been regarded as muscular. The oblique markings are generally 

 more distinct in the neighbourhood of the head, and I have seen 

 similar appearances in other nematodes in cases where I could not 

 at all feel satisfied that they represented distinct fibres. It is now, 

 indeed, becoming more and more evident that these markings are 

 illusive, and not to be trusted. They are probably due to the 

 superimposed chitinous layer. I have seen them beautifully distinct 

 in the chitinous capsules of Trichina ; Mr. Bastian has seen similar 

 deceptive appearances in Dracunculus ; and Mr. Beck has recently 

 offered a highly- satisfactory explanation of these illusive phenomena 

 under other circumstances.* Dr. Eberth in his monograph on the 

 Nematoda has given an admirable figure of these characteristic ap- 

 pearances as they occur in the neighbourhood of the head of JEnop- 

 lus megopthalmus, but he evidently regards them as muscular. 



All the tissues of the body appear to be highly elastic and 

 contractile, but the true muscular system consists principally, if 

 not entirely, of four longitudinal bands, two dorsal and two ventral, 

 passing from one end of the body to the other. Histologically, the 

 bundles consist of large, long, fusiform, nucleated cells, which, 

 when cut across transversely, display an appearance of lines running 



* See a paper in the " Quart. Jonrn. of Micr. Science" for January, 1864. 



