Japanese Tricladida Maricola. i q 



•move rows. Generally the thichness of the musculature dimin- 

 ishes towards either end of the pharynx. Quite similar to any 

 other forms, retractor and protractor muscles pass from the 

 pharynx through the parenchyma to the muscular layers of the 

 body- wall, as already described. 



Intestinal System. — The intestine shows a characteristic 

 differentiation into an unpaired anterior and paired posterior 

 trunks, but it deviates in Ect. limull somewhat from the normal 

 type, as will be described later. In general, the anterior trunk 

 extends to a point in front of the brain and usually sends out some 

 lateral branches on either side, numbering 7 or 8 in Pr. lactea, 6- 

 9 in *S'^. trigonocephala and 8-10 in Ect. limuli. The first branches 

 occur in both Pr. lactea and St. trigonocephala, sometimes in front 

 of the brain. In ^S'^. trigonocephala the branches are subdivided 

 before reaching the lateral margins of the body ; while in the 

 ■ others they show little tendency to subdivide, except at their tips, 

 where they are sometimes hi- or trifurcate. The posterior trunks 

 proceed, one on either side of the pharyngeal chamber, towards 

 the posterior body-end, where they unite together only in the case 

 of Ect. limuli, but remain separate in others. They are provided 

 with numerous diverticulae which have even less tendency to 

 bifurcate than those of the anterior trunk, their number being 14- 

 18 in Pr. lactea, 10-15 in Si. trigonocephala and 14-16 in Ect. 

 limuli. 



Among the marine Triclads, Syncoelidium pelucidum Hallez 

 is known to me as exhibiting a union of the posterior trunks, the 

 trunks fusing behind the vestibulum. From the point of union 

 an unpaired stem possessing a few minute diverticulae on either 

 side proceeds towards the posterior body-end, much as in Dendro- 

 coelum naiisicaœ, a fresh-water species, in which the fusion is brought 

 about by a confluence of a pair of mesial diverticulae, and not by 

 a fusion of the trunks themselves. Behind the union, however, no 

 unpaired stem is seen in Ect. limuli, in which the trunks unite 

 together at the ends. Of course, the fusion is of a most different 

 nature from that found in Bd. Candida, in which it occurs between 

 imesial diverticulae, thus forming a connection between the trunks, 



