DESCRIPTIONS OF GENERA AND SPECIES 387 



pairs of these vessels, opening, however, not into the dorsal but into the supra- 

 intestinal vessel. In segments fourteen to sixteen there is a single pair only, 

 which are connected (as are the hearts) with both dorsal and supra-intestinal 

 trunks. After this segment and up to the one hundred and thirty-fifth there are two 

 pairs in each segment, and from thence to the end of the body only one pair again. 

 The external intestinal network is composed of capillaries not so uniform in diameter 

 as those of the internal network, and they do not form so close a network ; nor is the 

 network continuous as such from segment to segment. Branches put the two intestinal 

 plexuses into communication. With this network communicate the intestino-tegumen- 

 tary vessels. The long anteriorly-situated intestino-tegumentary vessels have been 

 already described among the principal longitudinal trunks of the Oligochaeta. From 

 the fourteenth segment onwards, according to BOURNE'S figures, there are a paired series 

 (one paii- to each segment) of corresponding vessels, which put the superficial intestinal 

 network into communication with the tegumcntal network. They are also connected 

 with each other, especially by a longitudinal infra-intestinal vessel. 



The term Peripheral network is applied by BOURNE to the vascular plexuses in 

 the skin and in the septa, and in fact in all the organs of the body except the 

 alimentary trunk. These networks are connected with the intestinal by means of 

 the intestino-tegumentary trunks already referred to, and with the dorsal and ventral 

 blood-vessels by means of the dorso-tegumentary and ventro-tegumentary vessels. 

 The dorso-tegumentary vessels exist in front of and behind the hearts. They also 

 co-exist with the four posterior pairs of latero-intestinal hearts, but not with the 

 anterior of these. There are branches, however, of the anterior hearts which may 

 morphologically correspond to the missing dorso-integumentary vessels. The ventro- 

 tegumentary trunks open into the ventral vessel a pair to every vessel except the 

 first and the eighth to the thirteenth, where are the hearts. 



Megascolex has no subnervian blood-vessel. 



(40) Megascolex albidus (MICHAELSEN). 

 Periehaeta albida, MICHAELSEN, Arch. f. Nat., 1892, p. 337. 



Definition. Length, 135 mm.; number of segments, 110. No pigment in skin. Setae, 40 per 



segment. Dorsal pores commence V/VI. Clitellum, XIII-XVII. One genital papilla in 



middle line of XVIII, and a pair on IX and two pairs on X. Gizzard in VI ; septa 



1 1 I XIV thickened. Sperm-sacs in IX, XII. Spermathecae in VIII, IX, with a single 



diverticwlum. Hob. Marquesas. 



3 D 2 



