140 bulletin: museum of compaeative zoology. 



obliquely and dorso-ventrally through the blood spaces (PL 6, fig. 

 53). They surround the rhynchodaeum on every side, so that this 

 organ is held in place in the midst of the blood spaces by compara- 

 tively thin strands of tissue only. In the brain region they unite 

 into a pair of lacunae, which continue backward through the esopha- 

 geal region as the lateral vessels. These vessels are large and thin- 

 walled throughout the esophageal region proper and lie inter^ial to 

 the inner circular muscular layer (PI. 6, fig. 54), but pass outside 

 this muscle anterior to the nephridial region (PI. 7, figs. 55, 56). In 

 this respect the species is like Carinellci linearis. Shortly behind 

 the nephridial region the lateral vessels acquire muscular walls and 

 are strongly contracted at intervals. In a contracted condition they 

 appear to be surrounded by more parenchyma than is the case Avhen 

 they are distended (PI. 9, fig. 59). Throughout the intestinal region 

 they lie immediately beside the intestine and beneath the sexiial 

 glands. 



In the posterior esophageal region occasional diverticula of the 

 lateral vessels pass internally through the wall of the adjacent pro- 

 boscis sheath, and apparently spread out somewhat beneath the 

 epithelium of the latter, as has been described for Caeinella. 

 There are few of these diverticula, however, and they are with- 

 out regularity of arrangement. They appear rather like a spongy 

 network (PI. 7, fig. 55) with minute spaces than like definite ves- 

 sels. Posterior to the region wdiere the lateral vessels pass outside 

 the inner circular muscles are a few similar diverticular of the blood 

 vessels, and these i)ass through both the inner circular muscles and 

 the wall of the prol)oscis sheath. For a very short distance the 

 diverticula form a pair of rhynchocoel vessels, much like those in 

 Caeinoma but less conspicuous. 



Nervous system and se)ise organs. — The nervous system is much 

 as in Caeinella. Brain and lateral nerves are situated immedi- 

 ately outside the thin outer circular muscular layer, except for a short 

 distance behind the nephridial region, where they sink inward to 

 the midst of the longitudinal muscles, much as in Caeinoma. As 

 Avill be described Ijelow, they probably carry beneath them a portion 

 of the circular muscles, however. The brain is of fairly large size, 

 with well developed dorsal ganglia. The ganglia of the two sides 

 are widely separated as in related genera, and the dorsal and ventral 

 commissures pass directly beneath the basement layer as usual. 



