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E. R. HOSKINS 



of the gut free in the body cavity without a mesentery. This 

 space between the intestine and the dorsal wall of the body 

 cavity corresponds to the 'mesenterial fenestra' (Scammon '11). 

 This fenestra increases in size and extent during the later growth 

 of the embryo so that the gut lacks mesenteric support between 

 the middle of the spiral valve and the entrance of the duct of 

 the digitiform gland into the intestine. The mesentery is not 



D.GI. 



Fig. 9 XI. Dissection of a full term Acantnias embryo 220 mm. in length, 

 drawn from the left side. Ao., aorta; CI., cloaca; D.A., digitiform artery; D.A.A 

 and D.A.P., anterior and posterior rami of the digitiform artery; D.GI., digiti- 

 form gland; D.I. A., dorsal intestinal artery and vein; Mes., mesentery of intes- 

 tine Mes.D.GL, mesentery of digitiform gland; Mes. Fen., mesenteric fenestra; 

 P.V.I. , post-valvular intestine; Sp.V., spiral valve. 



The arteries on the digitiform gland were added to the drawing from another 

 specimen in which the vessels had been injected. 



really lacking, however, but attached to the digitiform gland, 

 which thus is supported from the midline of the dorsal wall of 

 the body cavity (fig. 9) . The mesentery of the digitiform gland 

 of the mature animal is thus quadrilateral in shape, with a long 

 edge fastened to the dorsal body wall, a short edge fastened to 

 the gland, a long oblique anterior border and shorter posterior 

 border perpendicular to the longitudinal axis of the body (fig. 



