BY JAS. P. HILL. 25 



tapers off gradually into the fibrous la3''er of the epidermis. That 

 of the ventral stem is more band-like in form, and laterally passes 

 over suddenly into the epidermic fibrous layer. In the cellular 

 portion of the dorsal stem gland cells are comparatively few in 

 number, while they are altogether wanting in the ventral. Of 

 the two stems the ventral is the more strongly developed, and 

 towards the posterior end of the body it remains more distinct 

 than the dorsal. 



In my preparations, and especially in the ventral cord, the 

 " stalked cells " of Spengel can readil}^ be distinguished. They 

 are elongated fibre-like cells with generally long deeply staining 

 nuclei. These cells are specially developed at the lateral margins 

 of the ventral stem. Their fibre-like basal processes traverse the 

 fibrous layer, while their outer ends converge towards the middle 

 line of the stem, thus enclosing a central space largely occupied by 

 the nerve cells. The nuclei of these latter are easily distinguish- 

 able by their large size and rounded appearance; they do not stain 

 very deeply, possess distinct nucleoli, and exactly resemble 

 the nuclei of the nerve cells in the collar cord. The nerve cells 

 lie immediately adjacent to the fibrous layer, and this fibrous 

 la3''er as well of the collar cord as of the trunk nerve stems is to 

 be regarded, according to Spengel, as made up of the ramified and 

 interlaced processes of these nerve cells. Here, as in the collar 

 cord, I have never succeeded in observing the giant ganglion cells. 



Trunk. 



( 1 ) Branchial r e g io n : As in all known species of 

 FtycJiodera. there is below the epidermis a delicate la3^er of 

 circular muscle fibres, in this species onl}^ a single fibre in thick- 

 ness. The longitudinal musculature internal to this is strongly 

 developed and as in the described species is interrupted dorsally 

 and ventrally by the vessel stems. The longitudinal musculature 

 of the outer wall of the genital wings is considerably stronger 

 than that of the inner wall. The latter is interrupted in the 

 region of the sub-median lines in whose course the openings of 

 the ducts of the gonads are situated. Numerous radial fibres 



