920 EXPLANATION OF PLATES. 



Fig. 25. Longitudinal horizontal section through the dorsal skin, shewing the 

 peculiar arrangement of the circular muscular fibres. (Zeiss A, Hartnack's camera.) 



PLATE 52. 



Fig. 26. Portion of ventral cord of Pcripatus capensis enlarged, shewing two 

 ganglionic enlargements and the origin of the nerves and commissures. (From a 

 drawing by Miss Balfour.) 



co. Commissures. E. n. Nerves passing out from ventral cords. F. n. Nerves to 

 feet. g. co. Commissures between the ventral cords containing ganglion cells, v. g. 

 Ganglionic enlargements. 



Fig. 27. Segmental organ from the 5th pair of legs of Peripatus capensis. This 

 nephridium resembles those of the 4th legs, and differs from all the others in its large 

 size and in the absence of any dilatation giving rise to a collecting vesicle on its external 

 portion (enlarged). The terminal portion has the same histological characters as in 

 the case of the hinder segmental organs. (From a drawing by Miss Balfour.) 



Fig. 28. Segmental organ or nephridium from the gth pair of legs of Peripatus 

 capensis, shewing the external opening, the vesicle, the coiled portion and the 

 terminal portion with internal opening (enlarged). (From a drawing by Miss 

 Balfour.) 



o. .?. External opening of segmental organ, p.f. Internal opening of nephridium 

 into the body-cavity (lateral compartment). s. Vesicle of segmental organ. j 1 . 

 Portion of segmental organ of 4th and 5th. legs, corresponding to vesicle of the other 

 nephridia. s. c. i. First or external portion of coiled tube of nephridium, lined by 

 columnar epithelium with small nuclei ; the cells project for very different distances, 

 giving the inner boundary of this region a ragged appearance, s. c. 2. Region No. 2 

 of coiled tube of nephridium, lined by small closely-packed columnar cells, s. c. 3. 

 Region No. 3 of coiled tube of segmental organ, lined by large flat cells with 

 large disc-shaped nuclei, s. c. 4. Region No. 4 of coiled tube of nephridium ; this 

 region is very short and lined by small columnar cells, s. o. t. Terminal portion of 

 nephridium. 



Fig. 29. " Portion of nephridium of the hindermost leg of Peripattis capensis, seen 

 in longitudinal and vertical section. The figure is given to shew the peritoneal funnel 

 of the nephridium. Portions of the collecting sack (s.) and other parts are also repre- 

 sented. (Zeiss B, Hartnack's camera.)" 



/./. Peritoneal funnel, s. Vesicle, s. c. i, s. c . i, s.c.$. Portions of coiled tube. 



Fig. 30. "Section through a tracheal pit and diverging bundles of tracheal tubes" 

 taken transversely to the long axis of the body. (Zeiss E, oc. 2.) (From a rough 

 drawing by Prof. Balfour.) 



tr. Tracheae, shewing rudimentary spiral fibre, tr. c. Cells resembling those 

 lining the tracheal pits, which occur at intervals along the course of the trachece. 

 tr. s. Tracheal stigma, tr. p. Tracheal pit. 



Fig. 31. "Sense organs and nerves attached from antenna of Peripatus capensis 

 (Zeiss, immersion 2, oc. 2.)" (From a rough drawing by Prof. Balfour.) The figure 

 shews the arrangement of the epidermis cells round the base of the spine. The spine 

 is seen to be continuous with the inner layer of the cuticle. 



