[29] OLTGOCH.ETOLOGICAL RESEARCHES. 907 



are all slightly puLsating, but none dilated nor differentiated enough t» 

 be called a heart. The laost posterior of them is the longest and the 

 most anterior one the most minute, just as in Telmatodrilus. 



The dermal vascular system is always composed of tertiary vessels, 

 mostly emitted from the perigastric vessels, and from them branching 

 into and between the dermal and muscular layers of the body. The 

 dermal vessels in Limnodrihis Hoffmeisteri are said to originate direct 

 from the ventral vessel, and from here extend between the layers of the 

 integument.* I have observed a dermal vascular system in Telmato- 

 drilus^ and in Gamptodrilus coralUnns, and Claparede in Limnodrilus 

 Udekemianus and Hoffmeisteri. 



The blood is always yellowish red, more or less dark in different 

 species. 



E— NERVOUS SYSTEM. 



The nervous system of Tubificidce resembles the same system of Lum- 

 bricttlidw and Encliytrceido^^ the former, however, more than the latter. 

 Along the ventral line of the body and closely attached to the same we 

 find the ventral nerve trunk, in the buccal segment branching itself, 

 forming the oesophagial commissures, again to connect on the upper 

 side of the body in the cephalic lobe with the suprapharyugial or 

 cephalic ganglion. 



This ventral ganglionic trunk is composed of two longitudinal and 

 parallel fibrous nerve truncs, more or less fused together, and in every 

 .segment surrounded by a ganglionic swelling or agglomeration of cellu- 

 lar ganglionic globules. The cellnuclei in this ganglionic substance are 

 mostly round and regularly defined ; only in Telmatodrilus we find them 

 more irregular, both in regard to their general form and to the smooth- 

 ness of their inclosing membrane. In every segment we find one pair 

 of lateral secondary nerves projecting from the ventral nerve cord. 



In Tubificini the fusion of the ventral fibrous nerve cords is nearly 

 jierfect, and the longitudinal space between them, when such one exists, 

 is never traversed by transversal commissures, so common in the true 

 Polychceta. In Te?mato<^n7*m, however, those nerve truncs are every- 

 where connected by numerous transversal and ramifying commissures. 

 Both truncs, however, are surrounded by the same ganglionic swellings, 

 no division in the same being perceptible (fig. 1 k ; PI. II). 



The most important differences presented by the nervous system of 

 Ttihificidoi result from the varying form of the cerebral ganglion, and 

 especially its anterior and posterior margins. The concavity of the 

 anterior margins seems in this family, as well as in LiimbricuUdce, to be 

 the rule, and in the species I have had opportunity to investigate I have 

 met with only one exception. In Spirosperma we find thus the anterior 

 margin to be considerably projected, the ganglionic matter here form- 

 ing a large conical processus, rivaling in size the rest of the cerebral 

 ganglion. 



*Claparede, Recherclies Auatomiques, p. 33. 



