III.] THE EARTHWORM. 245 



having, so far as is known, no direct communication with 

 the body-cavity. The larger trunks of this circulatory 

 system are five in number ; median longitudinal sitpra- 

 intestinal and supra and subneural vessels respectively, and 

 two small lateral neural ones. These are connected 

 metamerically in a manner described in the Laboratory 

 work (p. 261), and highly efficient capillary systems are 

 established in connection with them. In the segments 

 numbering seven to twelve, there exist two sets of vessels not 

 met with elsewhere. These are, firstly, a series of enlarged 

 crrwiMK$ophageaIiiG&&t\9 t 6 pairs in Allolobophora, 5 in Lum- 

 bricus, connecting the supra-intestinal and supra-neural 

 trunks ; secondly, a pair of lateral ctsophageal trunks, which 

 are connected with the supra-intestinal vessel alone (cf. 

 p. 260). The latter vessels are specially concerned with the 

 blood supply to the anterior portion of the cesophagus and 

 its calciferous glands. A condition somewhat exceptional in 

 the animal kingdom is met with in the blood vessels of the 

 ditellum, and less conspicuously of the body-wall generally ; 

 where the superficial capillaries pass up and ramify among 

 the actual epidermal cells themselves giving rise to an 

 epidermal blood plexus. The dorsal vessel contracts from 

 behind forwards and the circumcesophageal ones from above 

 downwards ; and there is reason to believe that the blood 

 which sets out to the parietes from both dorsal and ventral 

 median trunks, is returned to the vessels of the alimentary 

 system. The exact seat of origin of blood corpuscles 

 during life, to make good the loss of effete ones, is not yet 

 fully determined ; but it is highly probable that certain 

 appendages of the blood vessels known as " blood glands " 

 (p. 258) may be concerned in their production. 



