OF THE NEMATOIDS, P.iEASITIC AND FEEE. 577 



It has been named by Leuckart "mouth intestine" (Munddarm). Throughout the 

 rest of its extent, so far as I can understand Ebektii's description*, he says the oeso- 

 phagus is enclosed by a cellular organ which surrounds it on three sides, as an incom- 

 plete channel, leaving only the ventral surface free, and he looks upon this organ as 

 a special glandular body, though unfortunately he says nothing further with regard to 

 the actual structure of the oesophagus within the cellular development. I do not 

 know what Leuckaet's views upon the subject are, but to me it appears almost certain 

 that, although more or less constricted at intervals, the oesophagus in all these animals 

 may be considered a cylindrical organ with a central axial lumen, the ordinary trans- 

 verse radiating muscular fibres being almost wholly replaced by large nucleated cells 

 with granular contents (Plate XXVII. figs. 18 & 19). Whether muscular fibres exist or 

 not seems very doubtful ; I have never seen any, neither does Eberth speak of their 

 presence. The section of the lumen in Trichocephalus affinis seemed to me to have a 

 somewhat triangular form. In Trichosoma longicolle all the posterior portion of the 

 oesophagus is divided into elongated compartments by constrictions at intervals (Plate 

 XXVII. fig. 14). Near the centre of each compartment there appears a clear spherical 

 mass with no very defined bounding wall, whilst along the crenated margins a series 

 of similar though much smaller bodies exist, which are in all probability nucleoli 

 enclosed within an outer cell-wall, as are the similar bodies met with in the oesophagus 

 of Trichocephalus affinis (Plate XXVII. fig. 19). In this latter animal the rounded or 

 crenated borders are stiU better marked, and the cellular body with its enclosed spot 

 seen opposite each crenation, are in all probability the nucleus and nucleolus of a still 

 larger granule-containing cell whose walls are indistinct. In a very thin section which 

 I succeeded in making of this animal at about the termination of the anterior third of 

 the oesophagus, this organ was seen to. fill almost the whole width of the cavity of the 

 body (Plate XXVII. fig. 18), and to be made up entirely of an aggregation of nucleated 

 cells, each densely filled with granules, surrounding the small somewhat triangular central 

 lumen. I need not describe here the processes of a somewhat triangular shape, passing 

 from the parietal muscles of the body to the constricted portions of the oesophagus, 

 which are met with throughout a great part of its length, and act as a series of mesen- 

 teric processes, since most observers are agreed as to their presence and nature. In the 

 Trichocephalus affinis, although no demarcation of the oesophagus into large segments 

 exists similar to what I have described in Trichosoma longicolle, yet there do exist 

 large cellular bodies at pretty regular intervals, which seem homologous with the 

 clear non-granular mass present within each segment of the oesophagus in the latter 

 animal. Their structure is, however, different, since in T. affinis it consists of a clear 

 cell with no defined contents, save an excentric granular nucleus with its contained 

 nucleolus. These are very well marked towards the posterior extremity of the eso- 

 phagus. In the Trichocephali and Trichosomata, generally on either side of the termi- 

 nation of the oesophagus, there is a pear-shaped or more elongated prolongation directed 



* Untersuch. iiber Nemat. p. 50. 

 MDCCCLXVI. 4 L 



