70 



the membrane appears to consist of only one layer, but when torn in 

 different directions it is found to be composed of three or more layers 

 of a minutely fibrous texture, the direction of the fibres in which is 

 diagonal, so that they cross each other alternately. That the circu- 

 lar rugae are owing to wrinkles of the membrane and not to circular 

 fibres, appears probable from the fact that they disappear when the 

 worm is forcibly extended. Immediately within this elastic integu- 

 ment are found two fasciculi of muscular fibres, placed on the oppo- 

 site sides of the body, and which extend uninterruptedly from one ex- 

 tremity of the worm to the other. A portion of one of these fasciculi 

 is represented in Fig. 6, a. The muscular fibre is not marked with 

 transverse stria?. On each side of these muscular bands is a thin 

 tract of a peculiar substance, and in the middle of each of these tracts 

 is a more or less transparent line (Fig. 6", b, b). The substance com- 

 posing the tracts is minutely granular, and presents no other aspect 

 under the highest power I have been able to employ. The transpa- 

 rent line appears to be a canal excavated in the granular substance, 

 and is without visible walls. 



These tracts also extend from one end of the worm to the other, 

 and they are evidently analogous to organs of a similar appearance 

 present in the Aacaris lumbricoides, &c, and the function of which 

 is not yet I believe understood. They may probably be connected 

 with a nervous system, no other trace of which has been evident to 

 my observation. The longitudinal muscular fasciculi and the lateral 

 tracts of granular substance are placed between the outer and inner 

 membranes or tubes which constitute the body of the worm, and they 

 appear to be firmly adherent to the former. The internal tube is 

 constituted of a soft, pulpy substance, covered with a delicate mem- 

 brane. It forms numerous lobular, rounded folds or projections, 

 hanging as it were into the cavity of the body, as seen in the figure 

 of a transverse section of a portion of the body (Fig. 8), which affords 

 a lateral view of these projections, and (Fig. 9), which represents 

 them as seen from the inner surface. They are of a rounded form 

 and of various sizes, and present a homogeneous, minutely granular, 

 pulpy substance, filled with numerous minute, various-sized, more or 

 less globular, highly refracting particles (Fig. 11). These processes 

 apparently correspond to the analogous folds or nutritive processes, 

 as they are termed, of the Strongylus and Ascaris (appendices nour- 

 riciers of Cloquet). 



The cavity of the body thus circumscribed by these lobular folds 

 contains a pultaceous material, in which are imbedded the innume- 



