56 ART. 4. — N. YATSU : 



as far forward as the ventral lobe of the liver, while on the 

 dorsal side it is greatly restricted since the greater part of this 

 region is occupied by the dorsal lobe of the liver. In subsequent 

 changes this part of the alimentär}' canal attains a greater length. 

 It should be noted that in the larva referred to as No. 3, Simroth 

 ('97) has apparently mistaken the mid-gut for the Anlage of the 

 liver (p. 6.). 



From the 6 p. c. stage onward to the oldest sedentary larva 

 (15 p. c. stage) which I was able to study, a pit is found at the 

 bottom of the mid-gut (PI. V., Fig. 80, PI. VI., Figs. 83, 84, 

 and PI. VIL, Figs. 91, 93, pt.). A narrow passage way into 

 the intestine is seen at the bottom of the pit (PI. V., Fig. 80). 

 The fate of this pit is as yet unknown to me. 



The intestine seems to arise at the 4 p. c. stage by the 

 constriction of the liver. No difference in structure can be noticed 

 between the intestine and the liver (PI. V., Figs. 75, 80, and 

 PI. VII., Fig. 103., int.). Afterward it conies to be composed 

 of a thin epithelium (PI. VIL, Fig. 104, int.). It increases in 

 length until it meets the body wall about in the middle of the 

 latter. Then the ectoblast actively proliferates cells at the place 

 of contact, and these soon cause the tip of the intestine to become 

 attached there (PL VI., Fig. 85, and PI. VIL, Fig. 104). The 

 ; unis opens to the exterior at the 8 or 9 p. c. stage. 



The whole digestive tract just described is covered on the 

 outside by a thin flat epithelial layer, which is the visceral layer 

 of the mesoblast. 



In larvœ of the 6 p. c. stage an oedematic swelling of the 

 visceral layer of the mesoblast at the posterior portion of the 

 alimentary canal is often met with in fresh material (PI. V., 

 Fig. 80, and PI. VIL, Fig. 118, * ) as well as in stained 



