NERVOUS SYSTEM. 81 



audessous des couches sous-cutanees," as already described (Plate X, fig. 3). He mentions the 

 presence of distinct walls to these vessels, which, however, he learned from Borlasia anglice, 

 and in this I concur (Plate X, figs. 2 and 3). The walls are highly contractile, and in the 

 latter figure the vessels have been cut just before they complete the cephalic arch ; they are 

 observed to be surrounded by a ring of finely granular texture. M. de Quatrefages likewise 

 states, that though fixed in front the vessels are elsewhere free, and only connected here and there 

 to the body- wall by ligamentous bridles ; and in one of his plates he figures the ova between the 

 lateral vessels and the wall of the body. All our transverse sections show that such could hardly 

 occur, for the vessels occupy a secure position beneath the nerve-trunks ; and while the ovaries or 

 sperm-sacs sometimes press the vessels downwards towards the ventral surface, and increase the 

 distance between them and the nerve- trunks, they never actually intervene between the latter and 

 the body -wall in the perfect worm. This author appears to hold similar opinions still, since he 

 reproduces several of his former figures in his recent 'Anneles/ 



Many of the older naturalists confounded the ganglia with hearts, such as Ehrenberg, Schultze, 

 Huschke, Delle Chiaje, Duges, (Ersted, and more recently our countrymen, Drs. Williams and 

 Johnston. The latter mentions that the only blood-vessel he has seen is one " winding down the 

 middle, along the surface of the alimentary canal," but he can neither trace its origin nor termina- 

 tion. Dr. Max Schultze, at first, seems to have mistaken the edge of the proboscidian sheath under 

 pressure for the circulatory system, which he figures as two long straight trunks on each side of 

 the digestive tract. The true blood-vessels he describes as pertaining to the water- vascular system, 

 but shows neither beginning nor ending, though numerous large branches are represented as issuing 

 from them throughout their course. In a subsequent publication he endeavoured to reconcile his 

 early views with more modern, but fell into considerable confusion. Professor Keferstein does not 

 distinguish with sufficient clearness the different blood-systems of the Enopla and the Anopla; 

 and, indeed, applies the definition of the former to the latter ; but so far as they go his descriptions 

 and representations of the arrangement in this group are good. He, moreover, shows an 

 elaborate series of minute transverse anastomosing vessels in his Borlasia splendida, the structure of 

 which therefore differs from that usually exhibited by the British Enopla. M. Claparede, though his 

 publication is more recent, is less correct than the latter author, for he figures the dorsal vessel 

 coursing above the ganglionic commissures before giving off the anastomotic to join the lateral, and 

 thus a somewhat stiff square is formed in the cephalic region, while the lateral vessels have to pass 

 to the outside and front of the ganglia before meeting the anastomotic. The vessel appears also 

 to be placed on the dorsum of the proboscis. 



8. Nervous System. 



a. Ganglia. 



In the living animal two carmine, pinkish, or reddish colorations are observed on the snout, 

 some distance behind the tip : these mark the position of the cephalic ganglia or nervous centres 

 in most of the Enopla. As previously mentioned, not a few authors, misled by their colour, 

 pronounced them to be hearts. Under a lens they are somewhat pyriform, and each consists 

 of two divisions — a superior, shaped somewhat like an almond, and an inferior, continuous with 

 the great nerve-trunks. The superior lobe is connected with its fellow of the opposite side by the 



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