84 



HISATO KUWANO. 



glomeruli exist ; just posterior to the circular vessel, another circular 

 vessel, thicker than the former, goes round beneath the epidermis of the 

 trunk making a loop in the genital pleurae 1 (Fig. 5, cv. 2 .) ; lateral vessels 

 stand in communication with the dorsal vessel and the capillarise of the 

 gut wall, directly behind the last pair of the gill-pouches.- (Fig. 6, Iv.) 



Characteristics by which this species is distinguished from all other 

 Enteropneusts are as follows : — 



(1.) Definite arrangement of the longitudinal stems of the dermal 



capillaries in the anterior portion of the proboscis wall. 

 (2.) Occurrence of an alveolar structure in the connective tissue of 



the proboscis cœlom. 

 (3.) Occurrence of another circular vessel at the anterior portion of 

 the trunk, immediately behind the circular vessel lying between 

 the collar and the trunk. 

 (4 ) Confluence of the most anterior four pairs of the gill-pouches 

 into a common cavity, on each side, to discharge to the exterior 

 through a common gill-pore. So, the collor-pores find theml 

 selves at the anterior wall of the common cavities. 

 (5.) Communication of the lateral vessels with the dorsal vesse- 



immediately behind the last gill-slits. 

 (6.) Occurrence of circular muscle fibres at the anal region, just 



external to the longitudinal muscle fibres upon the gut wall. 

 (7.) Dorso-terminal position of the anus. 



Finally, it may be of interest to mention that though this 

 species is to be ranked, from its general structure, under the 

 genus Balanoglossus Delle chiaje among the Ptychoderidae, the 

 structure is associated, as already pointed out in foregoing foot 

 notes, with other structures characteristic for the members of 

 other groups of the Enteropneust (cf. p. 3. 5 and 6.) 



1. ) Occurrence of such a vessel is only case among known Enteropneusts. 



2. ) Such a communication does not seem to have been established in any other species. 



