A NEW SPECIES OF PENTASTOMUM. 169 



in most cases they are only almost one-third the size of these. They contain a 

 finely granular protoplasm, and a small spheroidal, ovoid, or somewhat irregu- 

 larly shaped nucleus. They are packed closely together, and occupy the whole 

 space between the subcuticular epithelium and the longitudinal muscle bundles. 



Among them are scattered the large glandular cells which will be described 

 as part of the secretory apparatus (see p. 178) ; and they are traversed by many 

 of the muscle-fibres, which will also be described in a special section of the 

 paper. 



Towards the body cavity this layer, or the longitudinal muscle-bundles 

 where they interpose, is marked off in the sections by a clear definite line, 

 which becomes deeply stained. This I take to be the ccelomic epithelium 

 (endothelium), but unfortunately none of my specimens were sufficiently well- 

 preserved to enable me to speak with confidence on this point. 



The Muscular System. 



When the animal is opened by a median dorsal incision, and the body-wall 

 spread out and examined from within, an appearance is seen such as is shown 

 in PL XXVII. fig. 17. 



Longitudinal bands are crossed by transverse bands, and interspaces, 

 roughly speaking, rectangular in form, are left between them. The ventral 

 median line is marked by a series of square gaps, towards the margins of which 

 are placed a number of radiating fibres. Along the lateral sides of the suc- 

 cessive squares there stretch two broad bands (fig. 17, m.l', m.l'), which are com- 

 posed of longitudinal muscular fibres, and, though somewhat variable in their 

 breadth, are nearly as wide as the squares. Beyond these, again, are a number 

 (commonly 8-10) of very much narrower longitudinal bands (fig. 17. m.l). 



A closer examination confirms the view that these longitudinal bands are 

 composed of muscular fibres, but the case is otherwise with the transverse 

 bands. These, as was pointed out by Leuckart, # are cellular in structure, 

 and consist largely of the glandular cells which will be alluded to when treating 

 of the subepidermic cell-layer (p. 178). They correspond with the external 

 annulations of the animal, and on focussing deeply through these bands the 

 stigmata are seen, whilst none are visible in the spaces between them. 



The muscular system of this parasite cannot, however, be fully understood 

 by means of such a preparation as has just been described ; to render our 

 knowledge complete, transverse sections are necessary ; and, when the informa- 

 tion derived from these is taken into account, there are seen to be present 

 three systems of muscular fibres — 



* Leuckart, he. cit, p. 39. 



