508 Cresswoll Shearer 



compression of the collar space and the great outg-rowth and 

 developnient of the anal region. The nephridial canals are short 

 and thiek (pl. 32 tig. 51) as coinpared with their conditiou in earlier 

 stages. The hcads of the ucphridia project inwards and forwards 

 into the collar haemocoel between the preseptal coelom and the 

 stoniach wall, here they end in short y-shaped branches not unlike 

 the nephridia of some Polychaets. To these brauched ends the 

 solenoeytes are attached, their tubes opening into the lumen of the 

 nephridial canals. 



In Ä. branchiata the heads of the nephridia are divided into 

 three such branches (pl. 32 fig. 52), termiuating in bell-like funnels 

 which are apparently closed. Into these bell-like funnels the tubes 

 of the solenoeytes project, as well as being attached to their lips and 

 sometimes the outside portions of the funnel. It is difficult in some 

 sections to make out if these funnels are really closed, and these 

 struetures undoubtedly bave given rise to the Statements about 

 the nephridia opeuiug into the blastocoel. In fig. 52, which is an 

 accurate drawing of a section, they will be seen to be closed, 

 and I have never been able to find that they are ever open into 

 the blastocoel. 



It is well known that in the adult Plioronis there are two organs 

 that function as nephridia, which open into the oral and the anal 

 Chamber of the trank coelom respectively by means of large ciliated 

 funnels. Caldwell (3), Ikeda (14), Goodeich ill) and De Selys 

 LoNGCHAMPS (25) agree that the canals of the adult nephridia are 

 derived during metamorphosis from those of the larvai organs, which 

 subsequently acquire openings into the coelom, in the adult fuuction- 

 iug both as nephridia and as genital ducts. 



Of equal importance with the early growth of the nephridia 

 and the origin of the solenoeytes is their final fate. The adult 

 Organs acquire openings into the coelom comparatively late in devel- 

 opment in some manner unknow at present. If the openings of these 

 organs should be formed from growths of the coelomic epithelium, 

 tben these adult nephridia of Pharonis would rescmble the compound 

 ncpliridia of some Polychaets described by Meyer (19). 



It was my Intention on commencing tliis work to follow in 

 detail if possible the growth of these coelomic funnels, but lack of 

 material lias rendered this impossible although I made it a special 

 l)oint to ol)tain material that might show the growth of these funnels. 

 Their formation must evidently take place rapidly, the criticai stage 



