124 A. J. CARLSON. 



luscs. This is, in a great measure, due to the difficulty in making 

 out the homology between the ganglia and their connectives in the 

 different groups, but also to the fact that names have been in- 

 vented with sole reference to the position of the ganglia, not to 

 mention the far-fetched homologies that have been made out be- 

 tween the molluscan and the vertebrate nervous systems. Thus 

 Alder and Hancock (1842) apply the terms " cerebro-spinal' 

 and "sympathetic" to the nervous system of the gasteropods. 

 Cheron (1866) endeavors to make out an analogy between the 

 stomato-gastric nervous system in the cephalopods and the sym- 

 pathetic system in the vertebrates. And Ransom (1884) applies 

 the term " vagi " to the two nerves from the pleuro-visceral gan- 

 glia to the cardiac and the branchial ganglia of Octopus. The 

 discrepancies in these homologies between the molluscan and the 

 vertebrate nervous system are so considerable that the introduc- 

 tion of the terms "cerebro-spinal," "sympathetic," "vagus," 

 etc., serves rather to confuse. Scarcely more commendable is 

 the introduction of names of ganglia with reference to their 

 position only. Thus Bottazzi and Enriques (1901) reject the 

 commonly accepted names "cerebral," "pleural' or " pallial ' 

 and "pedal" ganglia for the cesophageal nervous complex of 

 Aplysia, and substitute the terms "dorsal," "lateral," and "ven- 

 tral >: ganglia respectively. These names fit the conditions in 

 Aplysia admirably ; but how will they apply to PlenrobrancJicEa, 

 in which the pleural and the cerebral ganglia are fused into one 

 ganglionic mass situated dorsally, or to the Dorididae, in which 

 both the cerebral, the pleural, and the pedal ganglia are fused 

 into one ganglionic mass situated dorsally with reference to the 

 oesophagus ? It is plain that if we were to follow the principle 

 suggested by Bottazzi and Enriques, different names would have 

 to be invented to fit the conditions in the different subdivisions 

 of the gastropods, and frequently even for different genera 

 within the same group, because the position of some of these 

 ganglia is subject to considerable variation. This objection ap- 

 plies also to the term " subanal," which is used by Lacaze- 

 Duthiers (1859) for the ganglion commonly known as the vis- 

 ceral ganglion in the Haliotidoe. 



Bottazzi and Enriques reject the names, cerebral, pleural or 



