142 nVAJI TKEDA. 



of the body, the ventral vessel and the mesentery do not 

 end with the nerve-cord, but run a little further over the 

 ventral surface of the rectum, very near the anus (see 

 fig. 8), so that they recall a feature somewhat resembling the 

 rectal mesentery known in some forms of the genus 

 T h a 1 a s s e m a . 



About 15 mm. behind the external aperture of the ovi- 

 duct (o. (I., fig. 9) the ventral vessel gives off the neuro- 

 intestinal vessel {n. i. v.), Avhich is remarkably long, being 

 0"70 mm. The extraordinary length of the vessel is, as 

 referred to before, correlated to the reversed posterior 

 position of the junction of the fore-gut with the mid-gut, 

 to which the vessel under consideration finds its first 

 attachment. A short way off (about 5 mm.) from this 

 attachment the vessel becomes split into two long branches 

 20 mm. long, which run parallel to, but entirely apart from, 

 the intestine. They are, however, connected to the colla- 

 teral intestinal (c i.) by means of a series of numerous 

 delicate muscle-fibres, which frequently branch towards the 

 vessels and end mostly with a small nodule-like swelling firmly 

 adhering to the surface of the vessels (see fig. 9) . It is greatly 

 to be regretted that these two vessels could not be traced com- 

 pletely owing to the destruction of part of the mid-gut. 



It is not less interesting to note that the dorsal vessel 

 does not arise, in the usual way, from the mid-gut, where 

 the neuro-intestinal branches are attached, but it originates 

 from a part of the fore-gut about 50 mm. anterior to the 

 beginning of the collateral intestine (see d.v., fig. 9). Under 

 these conditions, and since the hinder portion of the fore- 

 gut passes close to the pharynx (/'/<.), the dorsal vessel 

 has to run a very short way (about 10 mm.) to reach the 

 pharynx. At the point where it reaches the gut, the dorsal 

 vessel is seen to pass over to two villi-like ridges lying 

 side by side and directed posteriorly. No doubt these 

 structures are a part of the so-called heart, which in the 

 present case is not seen as such. Very probably the heart 

 may be present as a diffuse sinus-like space in the gut-walls. 



