laxder: anatomy of hemiurus crexatus. 7 



tile elements or fibres formed by each myoblast, and each fibre remains 

 connected to it by a protoplasmic process. In the other case the contrac- 

 tile substance is formed in the entire periphery of the spindle-shaped 

 myoblast, thus enclosing the body of the cell. Each cell in this case 

 results in the formation of a sinojle fibre. 



Poirier ('85) describes and figures groups of cells found in Distomum 

 insisrne and D. megnini, similar to the subcuticular cells of Hemiurus 

 crenatus, and states that they are probably of a glandular nature, though 

 he was unable to find any traces of ducts. 



Prenant ('86) describes a peripheral granular layer of parenchyma in 

 Distomum (Lecithorchium) rufoviride which is very similar to that pres- 

 ent in Hemiurus crenatus. He regards it as a protoplasmic myogenic 

 layer, which, though provided with groups of nuclei, is not in a cellular 

 condition, and he feels compelled to conclude that muscle fibres have 

 been formed by a differentiation en bloc of the myogenic protoplasm. 

 The conditions found in Hemiurus crenatus differ from those found by 

 Prenant, in that each nucleus, or group of nuclei, is surrounded by a 

 definitely limited mass of protoplasm, which is distinct from the granular 

 layer, so that these nuclei cannot in this case be regarded as the nuclei 

 of the granular parenchyma. I am unable to offer any satisfactory 

 explanation of the source of this layer, but it certainly cannot be regarded 

 as the cytoplasm of the nuclei of the cells imbedded in it. According to 

 other investigators, as mentioned above, the muscles of the body wall are 

 developed from cells which remain as the giant cells. 



Juel ("89) in his description of Apoblema excisum, A. appendiculatum, 

 and A. rufoviride, does not mention anything which would correspond to 

 the peripheral granular layer of Hemiurus crenatus, but finds in each 

 species underneath the entire body musculature smaller or larger groups 

 of finely granular cells, similar in appearance to the subcuticular cells of 

 Hemiurus crenatus. He believes the function of these cells is to furnish 

 nourishment for the cuticulur and the muscle layers. 



Stafford ('96) describes somewhat similar cells, which he terms periph- 

 eral parenchyme cells. They appear exactly like the cells of the embryo, 

 the protoplasm being hyaline. He also finds cells that show a transition 

 from these to the ordinary parenchyma ; he thinks it possible that some 

 of the peripheral cells metamorphose into glands. 



Pratt ('98) finds in young Apoblema appendiculatum immediately be- 

 neath the muscles of the body wall a more or less scattered layer of cells, 

 which are oval or pyriform in shape. He terras them submuscular cells, 

 and is of the opinion that they are unicellular glands which furnish a 



