ON TEMNOCEPHALA. 287 



but its existence in the latter species has been denied by 

 Mace. 1 The layer of oblique muscular fibres found in the 

 body wall of some Polystornidse, though absent in others, is 

 not here represented. 



The interstices between the various organs and the wall of 

 the body are occupied by the parenchyma, which consists of a 

 variety of areolar fibrous tissue with very delicate anastomosing 

 fibres with plates and nuclei. In the interspaces of this 

 network are occasionally cells which having no distinctive 

 character may be called parenchyma cells ; but these only 

 occur irregularly and are entirely absent in many places. To 

 be regarded perhaps as modified cells of the parenchyma is a 

 layer of very large cells (PL XXI, figs. 3 and 4) lying 

 between the longitudinal layer of muscle of the body wall and 

 the testes, and extending from the region of the pharynx in 

 front to that of the genital aperture behind. These are the 

 subcutaneous gland-cells whose function is the secretion 

 of slimy and viscid matter to be discharged on certain areas of 

 the outer surface. The fibrous tissue of the parenchyma 

 forms wide meshes in which these cells are contained. The 

 cells themselves are of colossal size, averaging '066 mm. in 

 diameter, with a large vesicular nucleus like that of an ovum, 

 and a spherical solid-looking nucleolus. The substances of 

 the protoplasm of these cells presents three principal modifica- 

 tions. In the first of these forms there is only a very delicate 

 protoplasmic network in which the threads have a tendency to 

 radiate outwards from the nucleus to the periphery. In a 

 second form there occur in the interstices of the network a 

 greater or smaller number of rounded granules, '004 mm. in 

 diameter. In the third variety the place of the network is 

 more or less completely taken up by numbers of bacilliform 

 bodies, about '02 mm. in length, slender, and with a slight 

 enlargement at one end. Intermediate stages between the 

 two last forms are also to be observed, the contents of the cell 

 consisting of oval bodies, each of which is enclosed in a clear 



1 " Recherches auatomiques sur la grande douve du foie (Distoma 

 bepaticum)." [Abstract in ' Zool. Jaliresb.,' 1882, i, pp. 230, 231.] 



