226 DORYMENIA PERONEOPSIS. 



well-defined muscle bundles (Plate 7, fig. 6) which are attached to its wall and 

 on the other hand are fastened to the two pairs of globular radular supports 

 located beneath the posterior end of the radular sac. The bUnd extremities 

 of the radula and the ventral diverticulum are thus closely bound together. 

 It is probable therefore that the contraction of the circular muscle sheath results 

 in a lessened diameter and an increased length of the diverticulum whose free 

 extremity is thus pushed forward into the anterior section of the pharynx. 

 This process is doubtless aided by the action of two pairs of muscles that appear 

 to act as protractors. The more conspicuous of these is attached to the globular 

 radular supports and extends forward, expanding in a fan-Uke fashion, before 

 becoming inserted in the radular sac (close to the exposed teeth), the adjacent 

 wall of the pharynx and to a greater extent in the anterior end of the ventral 

 diverticulum. The second pair of protractors is relatively small, and from their 

 insertion in the circular coat of the mid section of the diverticulum extend forward 

 and downward to become attached to the ventral wall of the small cul-de-sac 

 into which the ducts of the ventral saUvary glands open. The retractors are 

 likewise four in number. The first and most posterior pair is attached to the 

 median radular supports and extending posteriorly and ventrally unites with 

 the body wall. The more ventral pair is attached to the ventral diverticulum, 

 close to the insertion of the ventral protractors, and after pursuing a ventral 

 and backward course alsp fuses with the somatic musculature. 



The stomach-intestine presents no especial features of interest beyond 

 what is sufficiently illustrated in the reconstructions of the anterior and pos- 

 terior ends of the body (Plate 7, fig. 5, 7). A well-developed, non-sacculated 

 anterior coecum extends from the termination of the pharynx to the brain region. 

 The main gut is provided with the customary cihated tract adjacent to the 

 gonad, and elsewhere is furnished with high columnar cells charged with a 

 granular secretion which is periodically discharged by constricting off the distal 

 extremities of the cells. In the region of the pericardial cavity the sacculations 

 disappear, the gut becomes approximately circular in outline and as a relatively 

 wide canal opens into the cloacal chamber. 



The pericardial cavity is a comparatively large space typically located in 

 the posterior end of the body. The heart likewise is well developed (Plate 7, 

 fig. 7), and is fashioned into two chambers communicating by a narrow pore 

 apparently guarded by a valve. The posterior division, presumably the auricle, 

 is comparatively thin-walled, distinctly less so than the anterior division, and 

 both are spanned by deUcate trabecular muscles. 



