44 THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITANNIAE. 



receptaculum seminis. This arrangement will be rendered intelligible by taking into con- 

 sideration the mode of origin of the receptaculum seminis, as given on p. 11. 



i. infundibulum. i. o. common orifice of the infundibula putting latter in communication 

 with the ovary, r. s. receptaculum seminis. t. p. peritoneal investment, u. uterus. 



Fig. 18. Transverse section through the ovary of a female embryo belonging to my 

 Stage XI, to illustrate the exogenous growth of the ova. The ovary is attached in a sessile 

 manner to the pericardial septum above which (in the figure to the right) the heart is seen 

 in section, and below (at the upper left-hand corner of the figure) a portion of the wall 

 of the rectum. 



Fig. 19. Dissection of adult male (V). The coiled vasa efferentia are succeeded by the 

 uncoiled vasa deferentia which pass backwards to the posterior region of the body and then 

 bend under the nerve-cords to meet in the mid-ventral line below the pygidial bulbus. The 

 right genital duct passes below the intestine. Through a short portion of its course the 

 rectum is held in position by a paired ligament (see Fig. 20). The convolute portion of 

 the left pygidial gland is removed. The posterior extremity of the body is represented as 

 being slightly tipped up to show the terminal organs. 



a. anus, g penis. I. s. v. left seminal vesicle. 1. 1. left testis. I. v. d. left vas deferens. 

 p. b. pygidial bulbus. p. g. pygidial gland, p. o. median dorsal orifice of pygidial glands. 

 r. s. v. right seminal vesicle. r. t. right testis. r. v. d. right vas deferens. v. n. c. ventral 

 nerve-cord. 



Fig. 20. Semi-diagrammatic section through a male (XII) taken immediately in front 

 of the last pair of legs in the region where the nerve-cords (united by a commissure) 

 approximate to one another before passing dorsally to meet together in the supra- rectal 

 commissure. The rectum is held up by paired ligaments. The vasa deferentia meet below 

 the nerve-cords in the median ductus ejaculatorius which is innervated (as is also the vagina) 

 by a special pair of genital nerves whose roots are seen to project from the two ventral 

 nerve-cords. The chitinous intima of the ductus ejaculatorius commences (or ends) slightly 

 posterior to this point. The heart lying in the pericardium is shown dorsally. 



d. e. commencement of ductus ejaculatorius. p. g. pygidial gland, r. rectum. 



Fig. 21. Similar section through same individual passing through the supra-rectal com- 

 missure. Above the latter lies the pygidial bulbus. The section is taken behind the last 

 pair of legs. 



d. e. ductus ejaculatorius. r. rectum. 



Fig. 22. Similar section through the anal segment, behind the supra-rectal commissure, 

 to show the 5 ectodermal involutions mentioned in the text, namely 2 dorsal, 2 ventro-lateral 

 and 1 median ventral lying over the ductus ejaculatorius. The ventral involution lies in the 

 angle made by the insertion of the penis into the body-wall and is the ventral organ of 

 the anal segment. 



d. e. ductus ejaculatorius immediately in front of the point at which it becomes eman- 

 cipated from the body-wall to project freely as the penis, e. o. ectodermal organs, p. b. pygidial 

 bulbus. r. rectum. 



