112 F. H. STEWART. 



PL 7, fig. 6), the middle gland extending further forward 

 than the other two. 



In the posterior intestinal region they lie ventral to the 

 intestine, in males in the grooves between the intestine and 

 the ductus. They pass on either side of the rectum, and 

 behind the level of the anus occupy almost the entire space 

 within the muscnlar wall. They open by a single pore on the 

 tip of the tail. On section, the protoplasm shows a highly 

 vacuolated appearance, the contents of the vacuoles staining 

 very uniformly, suggesting a colloid. The nucleus resembles 

 that of the ventral gland. 



The duct has a very fine membranous wall ; the contents 

 are basophil, sometimes acidophil. The three ducts remain 

 separate until a point immediately before the external pore. 

 There is, however, only a single such pore. 



Muscle or the Body Wall. 



The muscular layer is the thickest part of the body wall. 

 The cells which compose it are arranged in eight longitudinal 

 fields, four on each side, dorsal, dorsolateral, ventrolateral, 

 and ventral (PI. 7, fig. 8, dm, dlm, vlm, vm), separated from 

 each other by the four epidermal longitudinal lines and by the 

 four submedian lines. The latter, as I have stated above, are 

 not epidermal in 0. vulgaris, but are merely mesodermal 

 partitions. 



The entire eight fields extend forward to the anterior 

 extremity ; only four, the two dorsolateral and the two ventro- 

 lateral, reach the posterior, the two dorsal and the two ventral 

 ending at the level of the anus. In transverse section the 

 fields at the different levels show on the average the followinir 

 number of cells : 



(Esophageal. lutcstinal. Post Aual. 



2 . 1-2.0 



7 . 13 . 7 



7 . 14 . C 



6 . G . 



Buccal Eegion 



Dorsal . 1 



Dorsolateral . 4 



. Ventrolateral . G 



Ventral . 2-4 



The muscle-cells are of the usual Nematode type. I have 



