344 



ASAJIRÖ OKA ; ON THE SO-CALLED 



median tentacles open, according to Braem and myself, into the 

 cavity of the ciliated tubes, while CoRi maintains that they com- 

 municate with the lophophoral cavity by means of a canal outside the 

 tubes. Genu found an unpaired median bladder which neither Braem 

 nor I was able to discover. Lastly, CoRi observed without difficulty 

 the external o|)ening of the organ, which I confessed I could not find, 

 although I thought its existence most probable, while 1>kaem states 

 positively that there exists no such opening in reality. 



My Own Observations. 



rosition. In order to understand the real position whicli the 

 nephridium (jccupies in a ])oIypide, it is necessary to know exactly the 

 form and extension of the body-cavity. I will give here, therefore, a 

 short account of the organisation of a polypide as far as the b(jdy-cavity 

 is concerned, before going to the discussion of the subject itself. This 

 will serve at the same time as an explanation of the terms to be 

 employed hereafter. 



Eacli polypide has a more or less elongated cylindrical form, at 

 the distal end of which is fixed a, horseshoe- shaped lophoi)hore. For 

 the sake of convenience, the animal may be placed in sucii a manner 

 that the lophoj)hore comes uppermost, with its convex side directed 

 towards the observer and the various portions of the body may be 

 accordingly denominated as upper, lower, right, left, front, back, &c. 

 For the last two may also be used the words oral and anal from the posi- 

 tion of these openings. As is well-known, the cavity of the polypide 

 ccHnmiinicates freely at its lower end with the general cavity of the 

 colony, or the ccenœcial cavity of old authors, so that there is only one 

 continuous cavity in each colony. Towards the upper end, the form 

 of the l)ody-cavity becomes somewhat complicated, owing to the 



