ON A NEW rOLYGORDIUS FROM MISAKI. 



139 



The vascular system exhibits a general agreement with that of other 

 species — as for instance, of P. neapolitanus — except in one important 

 point. This consists in the faot that the consecutive 1 iterai loops, present 

 in a pair in each segment and which connect the dorsal and the ventral 

 vessel, stand on either side in open anastomosis with one another by 

 means of lateral longitudinal commissures. These evidently correspond 

 to the blind vessels known to exist in certain species (f. i., P. neapolitanus) 

 arising from a point midway in the course of the lateral loops. In the 

 present sp3cies, they come into communication with the lateral loops 

 towards which they are directed, instead of ending blindly before reach- 

 ing these. On each lateral loop it is seen that the commissure coming 

 from the loop directly in front finds its insertion at a point a short 

 distance ventral to the origin of the next posteriorly following commis- 

 sure. Therefore, the successive lateral commissures on either side of the 

 body do not form an uninterrupted longitudinal vessel, as does the 

 dorsal or the ventral vessel. — A pair of small vessels, arising from the 

 points where the ventral vessel sends forth the paired lateral loops, 

 seem to supply the intestinal wall. 



The species contain nearly mature ova or active spermatozoa as 

 early in the season as the end of March. 



The worms described live along the lowest tide-mark and in or on a 

 bottom consisting of shell-fragments, sand, pebbles and blocks of a rough 

 sandstone. They are exceedingly active creatures, constantly moving 

 the head-end and burrowing or creeping with remarkable ease. Not- 

 withstanding this nature, they are excessively frail and fragile, breaking 

 into pieces by the slightest cause or apparently even spontaneously when 

 kept in captivity. 



July 1st, 1903. 



