348 Mary R. Cravens and Harold Heath, 



are lined with a thin endothelium in which cell boundaries are 

 obscure but the nuclei usually distinct. Here and there, especially 

 in the posterior end of the animal, stalked cells are visible attached 

 to the wall of the blood vessel, and judging from their size and 

 general appearance are immature blood cells in process of formation. 

 Exterior to the endothelium a delicate basement membrane exists 

 and in a small number of favorable sections this is seen to be in 

 contact with a few small muscle and connective tissue fibres among 

 which are a few nuclei similar to the connective tissue elements 

 elsewhere in the parenchyma. 



Although we have examined repeatedly both cleared preparations 

 and sections, no sign of the kidney has come to light. At various 

 points in the head small cavities, lined apparently with epithelium, 

 have been located but thus far no connection has been traced between 

 them and the blood vessels nor with the exterior. 



Speaking of iV. mirabilis Veeeill writes (p. 448): '"On the ventral 

 surface of the head and occupying a large ovate patch on each side, 

 there is a group of small acute papillae, projecting slightly above 

 the surface; they are arranged in three or four irregular rows, and 

 are connected beneath the integument with pyriform organs which 

 can be seen by transmitted light as opaque bodies." These structures 

 number about 20 in each cluster and concerning their function a 

 note on p. 447 reads as follows: '-The precise nature of these 

 organs has not been ascertained, but they are probably special sense 

 organs." 



JouBiN (p. 5) notes the presence of these same organs in N. gri- 

 maldii but without any trace of the papillae noted above. The organs 

 themselves however are not unlike those described by Veeeill since 

 they are said to form "de chacque côté, sous la peau, un groupe de 

 gros globules blancs, sphériques, d'autant plus développés qu'ils sont 

 plus en arrière". Speaking of their probable use he adds "s'ils 

 avaient un pigment coloré on dirait, sans hésiter, que ce sont des 

 yeux, car ils sont à la place et ils ont l'apparence que ces organes 

 présentent d'habitude chez les Némertes. Mais, faute de pigment, 

 je ne puis conclure ainsi, et peut-être faut-il les considérer comme 

 des glandes céphaliques si communes chez les Némertes." 



In N. pelagica the same bodies exist in the head and open to 

 the exterior on the ventral surface. The presence or absence of 

 papillae, bearing the outer pore, is apparently a matter of small 

 moment since they are very sharply defined in one specimen and 



