EXCRETORY ORGTAX OF FRESH-WATER POLYZOA. 343 



Regarding that I made the following remarks : — '' Thei-e should be 

 some orifice by which they open outwards, for the high degree of 

 development they utt;iin prove that they are not useless remnants. 

 This makes me Aventure to assume the existence of minute i)ores, at 

 least on the two or three innermost tentacles of the anal side, pre- 

 sumably at their tips, although I am unable to produce any positive 

 proof." 



According to Cori (181*0), the body-cavity of Polyzoa, is divided 

 by an incompletely developed diaphragm into two portions, the lopho- 

 phoral cavity and the body-cavity s. str., Avhich correspond to the ' Pro- 

 somhohle' and ' Metasomhohle ' of PZ/oro/r/.s respectively. 'ï\\e nephri- 

 dium consists of two short ciliated tubes which open into a median 

 unpaired bladder-like sac, that communicates in its turn with the 

 exterior. " Die unteren Enden der l)eiden Kanäle, der Xiercnkanäle, 

 münden init weiten Offnungen, den Ne])hr()stonîen, zu beiden Seiten 

 des Ganglions in die Leibes (Metasom) höhle ein." The lumina of 

 the median tentacles are prolongations of tlie lopliophoral cavitv, being 

 connected Avith the latter by a sort of narrow channel running beside 

 the nephridial tubes. Such tentacles situated aljove the nephridium are 

 five in number (o. 2. 1. '2. o.) ; of tliese the three median ones stand 

 in no connection whatever Avith tlie latter organ, while the remaining 

 two communicate with it l)y means of the " Xehentrichter." The 

 author remarks further, that the e|)ist(3mal cavity open on both sides 

 in the lophophoral ca\'ity, c(,)ntrary to the statement of JjRaem. 



If Ave compare the above statements, we find that the chief points 

 of disaii-reement Avith refjard to the structure of the or^an are as 

 follows. The cavity inside the ciliated tubes is, according to Braeai 

 and myself, a. conti imation of the lophophoral cavity, Avhile Cori regards 

 it as a prolongation of the hody cavity s. str., ov the "Metasomhohle," 

 if we adopt his terminology. The lumina of a certain number of 



