514 J. PERCY MOORE. [Vol. X. 



In the seventh or ovarian somite the absence of chloragogue 

 cells (Fig. 15) permits the maturing ova to come into close con- 

 tact with the walls of the blood sinus, which they envelop — 

 a nutritive arrangement of importance. True chloragogue 

 cells are again absent in the tenth segment on the rectum, 

 which is covered by a layer of cubical peritoneal cells (Fig. 5). 

 In the region of the anus circular muscle fibres increase to 

 form a sphincter. 



The epithelium of the intestine presents the same general 

 characters as that of the oesophagus, but becomes more flat- 

 tened (Fig. 12 and 13), especially in the saccular enlargements, 

 while at the constrictions the elongated cells project into the 

 lumen to form valve-like outgrowths (Figs. 5 and 13). It is 

 ciliated only in the posterior part (Fig. 5). 



Vascular system. — The vascular system differs in no im- 

 portant respect from the description given of Branchiobdella 

 by Dorner and amended by Voigt. The peri-enteric blood 

 sinus, to which Voigt first specially called attention in Bran- 

 chiobdella, is highly developed in the present species, in which 

 it exists as a continuous space between the muscular and epi- 

 thelial coats of the intestine, extending from the third to the 

 eighth somites inclusive, and breaking up at each end into a 

 system of passages and lacunae having a retiform arrangement 

 (Fig. i). The sinus has an average depth of .005 mm. ; and is 

 without true walls other than the intestinal coats between 

 which it lies. It is crossed by numerous protoplasmic strands 

 and columns which bind its walls together, and remind one of 

 the stalactites and columns of a limestone cave. These be- 

 come larger and more frequent toward the ends of the sinus, 

 which they finally interrupt so much as to convert it into the 

 terminal plexuses mentioned. In Fig. 5, drawn from a speci- 

 men in which the sinus continued complete even into the 

 ninth somite, these strands are well shown owing to the ab- 

 sence of any considerable quantity of blood, which often stains 

 deeply and obscures not only the strands but the muscular 

 coat as well. Enlarged chambers exist here and there in the 

 course of the sinus ; and continuous enlargements extend 

 along the dorsal and ventral regions. The ventral or sub- 



