THE ANATO.MY OF ONCHOLAIMUS VULGARIS, BAST. 107 



0'0043 mm. J varying in sliape^ but more generally circular 

 in sections, the protoplasm scanty, nucleus splierical or 

 oval, 0"0032 mm., and staining- diffusely with basic dyes 

 (PL 7, fig. 8, To). In addition the lateral lines contain 

 gland-cells, but these will be described separately. Type 1 

 is most common. 



Where there is not much pressure from the bulk of internal 

 organs, as in the oesophageal and post-anal regions, the cells 

 project into the space between the body-wall and gut. Oppo- 

 site the gonads, however, they are very much flattened. In 

 the posterior oesophageal region Type 1 cells often show 

 vacuolation ; while in the median lines in the intestinal region 

 they are generally triangular on section, the apex directed to 

 the cuticle, and the protoplasm shows fibrillar passing in from 

 the subcuticula to surround the nucleus. 



The submedian lines (PI. 7, fig. 13, s.m.l.) are not epi- 

 dermal, but are merely mesodermal partitions between groups 

 of muscle-cells. 



Jagerskiold (10) describes epidermal sub-median lines in 

 neighbourhood of the nerve-ring in Cylicolaimus maguus; 

 nothing corresponding is present in our animal. InThora- 

 costoma acuticaudatum he mentions sub-median lines, 

 but does not make it clear whether they are cellular. The 

 subcuticula is an excessively fine sheet of protoplasm ; in fact, 

 in places it is so fine that it is impossible to demonstrate it. It 

 is continuous with protoplasm of the cells at the margin of the 

 longitudinal lines. 



De Man (12) in reference to the genus Oncholaimus and 

 more particularly to the species 0. fuse us, describes the 

 subcuticula as richly cellular and granular. Neither of these 

 statements applies to 0. vulgaris. 



I have used the term " epidermis " freely. I see no reason 

 why this structure in Nematodes should be veiled under 

 terms such as " hypodermis,'' etc., WandoUeck (15), Jammes 

 (7), and Hamann (4), are agreed as to its ectodermal origin. 

 The only authority who maintains its meso- dermal nature is 

 Zur Strassen (14). 



