92 THE ROYAL SOCIETY OF CANADA 



(16) I find figures this arrangement of muscles for two species of 

 Distomum; Wright and Macallum (17) also gives it for Sphyranura 

 Osleri; and Stafford (18) states that the parenchyma muscles come 

 to the surface to find insertion. 



Subcuticular Cells. 



The musculature of the body-wall follows directly below the 

 cuticle without the intervention of an epithelial layer (Figs. 6, 9 & 10). 

 Just below the circular muscles in between the longitudinal muscle 

 bundles are the so-called "subcuticular" or " chromatophile" cells. 

 These appear in section as little clumps of large deeply staining 

 nuclei surrounded by a small amount of protoplasm; in horizontal 

 section through these we find that they form a continuous network 

 like tissue. They occur over the whole body: between the muscle 

 fibres of the pharynx and of the posterior sucker, and around the 

 excretory and genital tubes for a short distance from their openings. 

 The oesophagus is surrounded by a dense mass of cells which look 

 as though they might be glandular in nature. However, staining 

 does not distinguish them from the subcuticular cells so I conclude 

 that they are essentially the same. Both the cells around the oeso- 

 phagus and those below the cuticle show slender necks of protoplasm 

 connected with the inner surface of the cuticle (Figs. 6 & 9). The 

 cells in the pharynx are more separated and show clearly prolongations 

 in various directions which join those from neighbouring cells and 

 so form a net work (Fig. 14). 



The nature and function of these "subcuticular" cells has been 

 variously interpreted. The majority of writers consider them to be 

 in some way the matrix of the overlying cuticle. W. B. Beham (19) 

 in Lankester's "Zoology" follows Blochmann (20) and describes 

 them as epidermal cells which have sunk in between the muscle 

 fibres so that only a narrow part of each cell is left in communication 

 with the cuticle. Ziegler (21) considers such an insinking of the 

 epithelium impossible as the layer of subcuticular muscles is fully 

 formed before the disappearance of the outer cell layer of the "Cer- 

 caria" larva. Brandes (22) and others call the cells in question true 

 unicellular glands whose function is to secrete the cuticle. In several 

 papers I find them described as the meristematic tissue of the body, 

 (Leuckart (23), Walter (24), Stafford (25)). Looss (26), in one paper 

 described them as remains of embryonic parenchyma with the function 

 of secreting the cuticle. Walter (24) ascribed to them two functions, 

 that of increasing and renewing the parenchyma, and of indirectly 

 nourishing the cuticle. Braun (27) described them as the most 



