OF THE NEMATOIDS, PAEASITIC AND FEEE. 563 



proper contractile portion. In A. lumhricoides, on the contrary, they are more deve- 

 loped than I have met with in any other Nematoid. In this animal they corre- 

 spond to the "appendices nourriciers" of Cloquet. The granular matter of the 

 muscle-cell is here enclosed on all sides by the contractile portion, except at one point 

 corresponding to its apex, and in this situation there is a bladder-shaped development 

 communicating with the medullary portion of the cell only by a more or less narrow 

 connecting isthmus (Plate XXIII. figs. 5, «, «& 8). There seems to be a direct conti- 

 nuity between the body of the cell and the simple fibres composing the parietes of these 

 bladder-like portions. In Ascaris lumbricoides these prolongations exhibit also a fibrous 

 network in their interior, amongst the meshes of which are contained numerous bright 

 highly refracting granules (Plate XXII. fig. 22). In Dracunculus medinensis these 

 internal fibres are still more developed into smaller and stronger loculi, in the midst of 

 which is situated the nucleated ceU (Plate XXV. fig. 16). From the surface of the 

 bladder in A. lumbricoides numerous delicate fibres are given off, which serve to connect 

 this with similar neighbouring processes, and with the axial intestinal canal in the first 

 part of its extent. 



The other kind of process arising from the muscle-cells consists of narrow band-like 

 prolongations, proceeding in a direction at right angles from the muscle-cell to the 

 adjoining dorsal and ventral median lines, where these are present. They necessarily 

 vary in length according to the distance between the longitudinal line and the muscle- 

 cells from which they emerge. They are the "transverse muscles" of De Blai>"ville 

 and Von Siebold, and the vessels or nerves of other writers. In Ascaris lumbricoides 

 their direction and arrangement can be well seen iu transverse sections. In this animal 

 some of the muscle-cells appear to give rise to transverse processes only, whilst in others 

 a bladder-like prolongation may be seen as well. These transverse prolongations are 

 composed of fibres and intermixed granules (Plate XXV. fig. 13), and are apparently 

 directly continuous with the body of the muscle-cells, as originally stated by Schneider, 

 though Walter* has since denied this. EBERTH'sf views are in accordance with those 

 of Schneider and myself. The nucleated cell of the medullary substance is situated 

 close to the origin of the transverse process, where this exists. In different Nematoids 

 a great variation is met with in the abimdance of the transverse processes, and gene- 

 rally they may be best studied, on account of their simplicity, in the Platymyarice. 

 Eberth has well represented them as they exist in Ileterakis vesicularis^, whilst in 

 Spiroptera obtusa they are less developed still, leading on to what obtains in other 

 Nematoids where they are absent altogether. This is the case according to Eberth in 

 Ox. ambigua and A. oxt/ura, and according to Schneider in Pelodytes strongyloides and 

 some of its allies. I have never met with them either in Dracunculus medinensis, or in 

 any of the free Nematoids. 



As before stated, in many Nematoids no median dorsal and ventral lines exist, though 



* YiKCH. Archives, 1860. t Untersuch. iiber Nemat. 1863, p. 67. 



t "Wiirzb. Naturwiss. Zeitsch. 1860, Erst. Bd. Taf. iv. 22. 



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