416 EDWIN S. GOODRICH. 



tentacles (8). I can confirm tliis author's discovery of the 

 two main longitudinal vessels, but not that of a tentacular 

 vessel. The dorsal vessel divides below the brain into two 

 branches, which run down on either side of the oesophagus 

 to join below, and behind the pharyngeal sac to form the 

 ventral vessel (figs. 17 to 21). 



Coelom. — Marion and Bobretzky described the spacious 

 coelom, subdivided by median dorsal and ventral mesenteries 

 and by transverse septa, and traversed by the oblique muscle 

 strands. Fraipont has figured the ccelom as filled with a fine 

 reticulum of stellate cells (2 and 3). It may be the case that 

 at a certain age, or at a certain time of the year, the cavity 

 of the body is so filled ; but I have never observed this con- 

 dition myself, and I am inclined to believe that Fraipont has 

 been somewhat misled by appearances brought about by the 

 coagulating action of fixatives, or by studying sections taken 

 in the region of a septum, or close to the head, where nu- 

 merous tissue strands extend from the anterior end of the 

 CBSophagus to the body-wall, as in worms generally. 



The wall of the intestine is covered externally with large 

 ii-regular cells projecting far into the coelom, and filled with 

 coloured granules (fig. 5). The coelomic epithelium lining 

 the other parts of the body-cavity is composed of cells, which 

 often are so filled with vacuoles that they project consider- 

 ably into the coelom (fig. 9). When a Saccocirrus is viewed 

 compressed under a cover-glass the body-cavity may appear 

 to be almost obliterated, but this appearance is deceptive. 



Head Cavity. — Amongst the most peculiar characters of 

 Saccocirrus may be reckoned the possession of a special 

 closed cavity in the head, consisting of a right and left 

 ampulla, situated in the peristomial segment, passing forwards 

 into canals which run up the prostomial tentacles (figs. 1, 2, 

 and 17). A transverse communicating canal runs across 

 beneath the posterior edge of the brain (fig. 16). The walls 

 of this system are provided with muscles — longitudinal in the 

 tentacular canal, circular as well in the ampulla. Its cavity 

 is filled with a fluid and lined by an epithelium. 



