66 W. BALDWIN SPENCEK. 



Fig. 26.— Longitudinal vertical section through the anterior end of another 

 male form. The section is cut so that the anterior end is nearly median, the 

 posterior more towards the side of the body. By this means the atrium 

 genitale is cut through, together with the side of the dilator rod-sac and the 

 vas deferens. The relationship of the latter to the ejaculatory duct and 

 vesicula seminalis is seen, and also the two arms of the latter. 



Fig. 27. — Longitudinal vertical section through the anterior end of the 

 mid-gut of a young female form. Immediately above this lies a special 

 glandular mass of cells, which has apparently no duct of any kind. Posteriorly 

 to the oesophagus lies the large nerve mass, and in front of the oesophagus 

 the nerve commissure is cut through. 



Fig. 28. — Longitudinal vertical section through the posterior part of the 

 body of a young female. The section is cut to one side, so as to pass through 

 the length of the oblique muscles, the insertion of which in the body-wall 

 is shown ; two bundles of fibres being with rare exceptions confined to 

 the space within each annulus. The parietal gland-cells are seen occupying 

 the lateral compartments of the body. The arrow points to the posterior end. 



Fig. 29. — Longitudinal vertical section through the mid-ventral line of the 

 body-wall of an adult female form. The section shows the arrangement of 

 the muscle-layers, a few oblique fibres being cut through. The stigmatic 

 glands are seen to be entirely confined in each annulus to the anterior portion, 

 which is marked off from the posterior portion by the presence most exter- 

 nally of a darkly staining ridge of chitinous material. 



Fig. 30. — A small portion of muscle-fibre from the muscle coating of the 

 rod- and cirrus-sacs in the male form. In and amongst the fibres is proto- 

 plasmic material, containing nuclei but no distinct cell outlines. 



Fig. 31. — Surface view of a small portion of the head highly magnified and 

 seen by reflected light to show the openings of the stigmatic glands, each of 

 which is surrounded by a raised circular rim. The dark spots seen probably 

 correspond to the bases of subcuticular cells. 



PLATE VI. 



Lisi of References. 



In Figs. 35 and 3G the numbers correspond to those used in the description 

 of the different nerves in the text. 



In Figs. 38 and 39 the numbers correspond and indicate the different 

 points of attachment of muscles, and in Fig. 39 the letters correspond to 

 those used in the description of the different hook-muscles in the text. 



B. Hk. Basal joint of hook. C(. Connective tissue. Cn. External cuticle. 

 E. Subcuticular epithelium. /. Moveable attachment of the hook to the basal 

 joint. Gr. Groove around oral papilla. Ilk, Hook. Hk. i. Invagination in 



