10 



ON A NEW SPECIES OF ENTEROPNEUSTA, 



The splanchnic epithelium continues on the surface of the 

 ventral septum which, as Spengel has shown, represents a median 

 fold of the ventral proboscis wall, and is connected at intervals 

 with the limiting membrane of the epidermis. The two ventral 

 l^roboscis pockets separated from each other by the ventral septum 

 are usually filled by a loose connective tissue; however, in some 

 cases, a distinct space bounded by this tissue may appear (fig. 12, 

 vp.) Behind the posterior free edge of the septum the ventral 

 pockets unite to form the ventral unpaired portion of the proboscis 

 ccelom. 



Exceptionally two folds may arise from the limiting membrane 

 of the epidermis to form the proboscis septum; the two folds 

 enclosing a median pocket between them unite with each other 

 along the mid-ventral line of the proboscis gut. Further pos- 

 teriorly the point of union of the two folds gradually passes 

 ventrally until the median pocket is obliterated, and the septum 

 assumes the normal condition. On the dorsal side the two 

 proboscis pockets separated by the heart bladder are in different 

 individuals of this species very varied in their relations. The 

 proboscis pore may be single or double, and occupy a median 

 position or it may be single and situated on the right side of the 

 median line. 



(a) In the majority of individuals the proboscis pore occupies a 

 median position (fig. 12, p.) and it may then be formed in three 

 ways — , 1 ) The two dorsal proboscis pockets may unite with each 

 other behind the heart bladder to form a single median proboscis 

 canal which opens by the median proboscis pore; (2) the left 

 pocket alone may form a proboscis canal, the right ending blindly; 

 (3) the right pocket may form the canal, the left ending blindly. 



{h) There may be two proboscis pores, the two dorsal pockets 

 giving rise to two proboscis canals (fig. 10, pc.) which both open 

 to the exterior (fig. 11, p.). 



(c) The proboscis pore may be single and open on the right 

 side; in this case the left pocket ends blindly while the right 

 continues posteriorly, taking an almost median position above the 



