368 PROCEEDINGS OF THE ACADEMY OF [May, 



join the stomach; each gland (which has been fiihy described by Gast) 

 has one large nucleus^ or as many as three nuclei evidently produced by 

 amitosis of the single one. The substance of these digestive glands 

 appears granular. 



Foot. — This has been carefully described by Gast, and I have little 

 to add to his description. It is immovably attached to the surface on 

 which the animal rests by the secretion of large hypodermal glands 

 which are apparent only in the free-swimming stage. Its outhne {F., 

 figs. 2, 3) is more or less circular and it is placed upon the ventral sur- 

 face of the body anterior to the cloacal aperture, its margin shghtly 

 elevated. 



Musculature. — A. vorax agrees very closely with A. lentiformis in 

 the details of the musculature, which is very strongly developed. The 

 following muscles may be distinguished (figs. 1-3) : 



I. Hypodermal muscles (muscles attached at both ends to the 

 hypodermis). 



(a) Circular muscles. 



(1) Sphincter coronse primus, Sph.C. I., a completely closed ring at 

 the edge of the corona with a dorsal loop (Gast's rm 1). 



(2) Sphincter coronse secundus, Sph.C. II, a narrower muscle just 

 behind the preceding, interrupted ventrally (Gast's rm 2). 



(3) Sphincter coronse tertius, Sph.C. Ill, a completely closed ring 

 (Gast's rm 3a). 



(4) Sphincter coronse quartus, Sph.C. IV, present onty dorsally and 

 not parallel to the other sphincters (Gast's mb of his fig. 2). 



(5) Sphincter coronse quintus, Sph.C. V, a slender muscle inter- 

 rupted dorsally and ventrally (Gast described it as a branch of his 

 rm 3). 



(6) Sphincter coronse sextus, Sph.C. VI, a completely closed ring 

 (Gast's rm 4). 



(7) Sphincter coronse septimus, Sph.C. VII, the largest of the coro- 

 nal sphincters, a closed ring giving on each side a branch to join the 

 next (Gast's rm 5). 



(8) Sphincter coronse octavus, Sph.C. VIII, with a shorter dorsal 

 and a larger ventral interruption (Gast's rm 6). 



(9) Sphincter trunci primus, Sph.tr. I, a small muscle, present on 

 each side dorso -late rally only, subject to considerable variation. 



(10) Sphincter trunci secundus, Sph.tr. II, interrupted dorsally only 

 (Gast's rm 7). 



(11) Sphincter trunci tertius, Sph.tr. Ill, interrupted ventrally and 

 dorsally (Gast's rm S). 



