PLATE I. 



Nervous system blue. Alimentary canal green. Heart and blood-sinuses red. 



Cloaca-ducts yellovv. Appendages of the cloaca-ducts brown. 



Integument, cloaca-wall, copulation-spicula, blood-gland, pericardium and muscles black. 



Fig. i — 22. Proneomenia Weberi. 



Proneomenia Weberi, 4 • ', drawn from spirit-specimens. 



Spicula 125 . A of the body-vvall, B cloaca-spicula, C spicula from the hinder body-region, 



D along the ventral groove. 

 Schematic sections along the lines AB — NO of fig. 11. 28 v. See text. 

 Reconstruction out of transverse sections of genital glands, pericardium, cloaca-ducts, part 



of the cloaca and digestive canal. Dorsal view. c copulation-spiculum. 28 

 Epithelium of the wall of the cloaCa-pouch /; (cf. fig. 5), a cavity in which a cloaca- 

 spiculum. 215 X- 

 Fip-. 13. Reconstruction of the anterior part out of longitudinal sections. p wall of the pharynx, 



a part of the mouth-cavity, enclosed by the "Mundleisten", in which the cirrhi are 

 found, b muscles of the pharyngeal fold. 28 X- 

 Figs. 14 — 16. Schematic transverse sections of the anterior part, cf. the lines AB — E F of fig. 13. 



S septum, cc cartilaginous cells of the radula. 28 ■ . 

 Fig. 17 A. A longitudinal section through the radula. a radula-sac, b epithelial pouch. See text. 37 X. 



B. A transverse section; the greater part of the teeth are broken. 2i7 X. 



C. Row of teeth of the radula, isolated with Eau de Javelle. 88 X. 

 Fig. 18 A. Transverse section through a cloaca-duct. 



B. Transverse section through the vesiculae seminales. 190 X. 

 Fig. 19. Transverse section through a copulation-spiculum with its muscular bundies. 125 X- 



Fig. 20. Longitudinal section through the base of a copulation-spiculum (see text). 150 X. 



Fig. 21 A. Idem. ƒ> protractors, r retractors. 28 X. 



B. Point and middle piece of a copulation-spiculum, isolated with Eau de Javelle. 125 X- 

 Fig. 22. 5 Transverse sections through the pericardium with the heart. 



A a the two distal pericardial invaginations, forming together : 



Ba the atrium. 



Cv the ventricle. 



D av the right atrio-ventricular opening, with little sphincter. 56 X. 



Figs. 23 — 40. Proneomenia longa. 



Fig. 23. Proneomenia longa, 4 • , drawn from the spirit-specimen. 



Fig. 24. Transverse section through the mouth-opening, along line A B of fig. 27. 24 X. 



Fig. 25. Papillae of the integument. 315 X- 



Fig. 26 A. Transverse section through the radula, 



B. A hooked tooth. 190 X. 

 Fig. 27. See plate II. Reconstruction of the anterior part, out of transverse sections. a part of 



the mouth-cavity filled with cirrhi ; b epithelial pouch of the radula. 24 X. 

 Transverse section through the radula in pouch /; (cf. fig. 17 A). 190 X- 

 Transverse section somewhat more distally; the teeth have disappeared; cuticular matter 



is forméd. 190 X. 

 Schematic transverse sections through the postenor extremity. 28 y. ag preanal gland, 



c s copulation-spiculum. 

 Transverse section through the heart. p pericardium, a atrium, bilobed, k invagination of 

 the dorsal pericardial wall, forming the ventricle more proximally, av left atrio-ventricular 

 opening with sphincter. 88 X- 

 Transverse section through the radula-sac. 215 X. 

 Epithelium of the dorsal cloaca-wall. 388 X- 

 Epithelium of the lateral cloaca-wall. 215 X. 



Transverse section through the posterior end of the second specimen, cf. fig. 33. es small 

 copulation-spicula. 25 X. 



