ox DEVELor:\rEXT ETC. OF piior.oxrs. ooö 



unpaired diverticulum ]n'otrucles itself forwards (fig. 14, dir.). The 

 position of the organ is wholly ventral to the œsophagus {œs.), 

 and the form is like that of a sac eomiiressed in the dorso-ventral 

 direelion ((igs. 4"), 4*.>, 50«, and 63 r;, div.). The iutcrnal cavity 

 is continuous with the stomach cavity. The roof of the diverticulum 

 in the fresh state generally shows a reddish hrown tint. This 

 coloration is (hie to the superposition of the fundamental brown- 

 ish coloui- on the hfemoglobin of the blood corpuscles which, in 

 advanced larvcT, overlie the organ in either one, or two masses. 

 The cells which compose the diverticular wall are tall and slightly 

 curved, and are ciliated on the free ends (fig. ÖO «, div.) In fully 

 grown larvœ of every type, each cell constantly contains a single 

 small round vacuole in its distal end (fig. <)! />). The vacuoles can 

 not ])e stained bv most of the staining reagents. I have seen 

 them in the diverticular wall of a highly advanced larva belonging 

 to type A, which had already evaginated the ventral ponch ; even 

 in this case, they were found only one in each cell (fig. 61 b).' 

 The whole of the diverticulum is lined externally with the thin 

 j)eritoneal layer (see the above figure). 



Many previous observers have noticed this organ and have 

 called it by various names : — 



J. MuLLER ('46)— " Blinddarme " (paired), 

 Gegenbalte ('54) — " Haufen der Leberzcllen," 

 Wagexer ('47) — " Leberblinddarme," 

 Clapaeède ('63) — " A dark mass with glol)ules " (after 



Mastermax), 

 Metschnikoff ('71) — " brown specks," 

 Wilson (A.G.) ('81)— ''glandular lobes of the stomach," 

 Masterman ('97) — " Xotochord " (paired), 

 TvOULE ('981 — " Isotochord " (unpaired). 



