808 ON THE MORPHOLOGY OF THE HELICINIDJE. 



Fig. 18. A section still more ventral than the above, showing the deepest part of the 



pericardium and its relation to the kidney. 

 ¥ig. 19. A more ventral section passing through the reno-pericardial canal, 



7'.p.C. 



Pig. 20. A similar section passing through the ventral part of the visceral mass. 

 Fig. 21. Part of a section slightly ventral to that drawn in fig. 19, showing the 



uropore, Ur.p., opening into the mantle-cavity. 

 Fig. 22. A section through the reno-pericardial canal. Magnified about 600. 

 Pig. 23. Part of a section passing through the uropore of Lucidella aureola and 



showing the character of the renal epithelium. X 960. 

 Pig. 24. A diagram reconstructed from the series of sections drawn in figs. 16 to 20, 

 showing the relations of the kidney, ureter, stomach, pericardium, and 

 mantle-cavity. 

 Pig. 25. The genital ducts of Alcadia hollandi $ . The lower half of the figure is 

 drawn as it appears when viewed by transmitted light, the upper part as 

 seen by reflected light. In this and in figs. 26-29, 40, and 41, the 

 gonaducts are represented as seen from the ventral side, after the wall of 

 the mantle-cavitjr has been cut throvigh by a dorsal incision and the 

 rectum and gonaducts turned over to the right side of the animal. 

 Fig. 26. The gemt-A\ dwciii oi Eutrochatella jjulchella $. 

 Fig. 27. The genital ducts of Aplianoconia mergiiiensis $ . 

 Pig. 28. The genital ducts of Palaohelicina idee. '^ . ' 



Pig. 29. The genital ducts of Oro6o_pAfl'«a^o»so«6r/» $. 

 Fig. 30. A longitudinal section through the genital ducts of Alcadia hollandi '^ , 



passing through the aperture of the hypobranchial gland. 

 Fig. 31. A longitudinal section from the same series, showing the aperture of the 



vaginal duct. 

 Ifig. 32. Another section from the same series, showing the origin of the oviduct 



from the ovarian chamber. 

 Fig. 33. Another section from the same series showing the connection of the vagina 



with the vaginal sac and ootype. 

 Fig. 34. Another section from the same series showing the opening of the oviduct, od., 



into the descending limb of the V-shaped tube, od.' 

 Fig. 35. Another section from the same series showing the receptaculum seminis 



opening into the ascending limb of the V-shaped tube. 

 Fig. 36. Glandular epithelium from the wall of the ootype of Alcadia Jiollandi. 

 Fig. 37. Ciliated epithelium and spermatozoa from the receptaculum seminis of 



Alcadia hollandi. 

 Fig. 38. A section through the oviduct of Alcadia hollandi. Highly magnified. 

 Fig. 39. An epithelial ridge from the bilobed caecum of the ootype of Orobophana 



/onsonbt/ir. 

 view of the genital ducts o{ Alcadia hollandi ,$ . 



Fig. 41. A similar view of the genital ducts of Aphanoconia gouldiana $ . 



Fig. 42. A drawing made from a combination of several serial longitudinal sections 

 through the genital ducts of Etitrochatella pulchella $ , showing the 

 narrow diverticulum, k.r., which may possibly represent the vagina of the 

 female and therefore be the homologue of the right kidney-sac. 



Fig. 43. A dissection showing the pedal, pleural, and visceral nerve-centres in 

 Alcadia palliata, with the principal nerves issuing from them. The 

 cerebral ganglia have been removed. The dissection is made from the 

 dorsal surface ; the foot, as is usual m contracted specimens, is turned 

 forward and lies in front of the head with the sole uppermost; the vi'alls 

 of the head and the mantle have been cut away, and the visceral mass has 

 been dissected as far as is necessary to show the course of the subintestinal 

 nerve and its branches. 



Fig. 44. The nerve-centres and principal nerve-trunks of Alcadia hollandi, viewed 

 from the right and above. The drawing was made with the camera 

 lucida, after removal of the nerve-centres from the body. 



Figs. 46-52. A series of transverse sections through the pleuro-pedal nerve-centres of 

 Alcadia hollandi, showing the principal tracts of nerve-fibres in the fused 

 pedal, pleural, and subintestinal ganglia. For a full description of these 

 figures, see the text, p. 789. The position of the pedal gland is indicated 

 in fig. 45. 



Fig. 53. The left cerebral ganglion of Palceohelicina idee, viewed from the inner 

 surface. The ganglion is stained with Mayer's hfemalum and drawn by 

 transmitted light ; 1, 2, 3, 4, the four labio-proboscidean nerves. 



Fig. 54. A similar preparation of the left cerebral ganglion of Alcadia palliata. 



