ON DEVEL0P3IENT ETC. OF PITORONIS. 587 



RouLE lias describod the nepliridia of the Inrva in n soine- 

 Avhat pecidiar way. Aceordini;" to him, tlie organs lie considerably 

 anteriorly as they are found on both sides (jf the stomach divcrti- 

 culnm, and are said to l)e constructed of cells forming a syncytial 

 mass which is attached to the somatic walls. No lumen and no 

 leading canal have been detected in these masses. But, if judged 

 from the author's text and figures, it seems to me highly pro- 

 bable that his so-called nepliridia correspond to the corpuscle 

 masses of other writers. Having overlooked the j^ostoral septum 

 and the true corpuscle masses, he seems to have come to mistake 

 the latter for nephridia. Thns, so far as I can understand his 

 description, he did not notice the change in position of the 

 organs with regard to the postoral septum during metamorphosis. 



As to the number and the ])Osition of the stomach diverti- 

 culum, the larva of Phoronis mbcdieri is described to be in the 

 same condition as that of P. ijbnal. But the vacuolization process 

 of the organ is in the former species moiv complex than in the 

 latter, thongli it is simpler than in the larva' studied by Master- 

 man. When these three cases are considered together, it may be 

 concluded that they indicate specific variations. 



Roule's '' cordon doi'sal," which is considered to show the 

 rudimentär}^ state of the rectum of the adult, has not been des- 

 cribed by any previous author, and also could not be detected in 

 any of the types of the larvie studied by me. If this " cordon 

 dorsal " be reconstructed from Roule's text and figures, it seems 

 to me almost without doubt that the structure referred to corres- 

 ponds to the dorsal vessel on the stomach. When Roule's figure 

 (75) and mine (58 c) are compared, both of which show a cross 

 section through the tentacular region at a similai- level, it will 

 be noticed that the " cordon dorsal " and the " vaisseau dorsal "' in 



