APLYSIA. 265 



Plate V. 



Fig. 16. General dissection of the nervous system from the 

 dorsal side. The stomato-gastric ganglia and 

 nerves are not shown. The branchial and genital 

 ganglia have been isolated from the organs they 

 innervate. Cerebral nerves 1, 3, 4, 6 are shown 

 on the left side, nerves 2, 5, 6 on the right. The 

 distribution of the first three nerves from the pedal 

 ganglion, all of which run ventral to the buccal 

 mass, is not shown. The remaining pedal nerves 

 are shown on the right side only, x 2-5. 



Plate VI. 



Fig. 18. Ventral view of the accessory genital organs. The 

 hermaphrodite gland and external portions of the 

 male apparatus are not shown. X 2-5. 

 Fig. 19. Dissection of male copulatory organ from the dorsal 



aspect. X 3. 

 Fig. 20. Scheme of the reproductive apparatus as seen from 

 the ventral side. The various portions of the 

 accessory genital mass have been separated to show 

 the course taken by the genital elements. The 

 external portions of the male apparatus are not 

 shown. 



(a) Transverse section of the large hermaphrodite 

 duct with the penis in situ. The section is 

 taken along the line a on the schematic figure. 

 In this and succeeding sections the dorsal 

 side of the section is uppermost in each case. 

 (6) Transverse section of the large hermaphrodite 

 duct along the line b, viz. : through the bursa 

 seminalis and entrance of the spermathecal 

 duct. 



(c) Transverse section of the large hermaphrodite 



duct along the line c. 



(d) Transverse section of the accessory genital 



mass along the line d. 

 In these sections note the travelling of the 

 seminal groove from ventral to dorsal sides of the 

 large hermaphrodite duct until in section c it no 

 longer lies in the wall of the duct, but passes over 

 into a fold from the wall. In section c there are 

 therefore three tracts within the large duct, viz. : 

 the oviducal portion and the seminal groove, both 



