ON THE NErUlUDIUM OF I'HYLACTOLAEMATOUS POLYZOA, 25 



Material and Metltods. The colonies were tii'tit stupetiecl with a iluid 

 prepared after the recept of Dr. Cori (10 7o sokition of methyl alcohol in 

 0.75 7o salt solution, with a few drops of chloroform) and then fixed with 

 Flemming's fluit. They ^vere then washed in running water and hardened 

 gradually in alcohol. For staining, I used lioehmer's Haematoxylin, some- 

 times in connection with alcoholic solution of eosin. The stupefying fluid 

 of the Prague naturalist seems to work especially well upon such forms as 

 Polyzoa, for I was able by its help to preserve the colonies with every poly- 

 pide fully protruded. As noticed at the beginning of the paper, all the 

 material I used for my study was of one species, namely Pectinatella 

 gelinosa Oka. 



Position,. In order to understand the real position which the nephridium 

 occupies in a polypide, it is necessary to know exactly the form and extension 

 of the body-cavifcy. So, I will give here a short account of the organisation 

 of a polypide so far as the body cavity is concerned, before going to the 

 discussion of the subject itself. This will serve at the same time as an ex- 

 planation of the terms to be employed hereafter. 



Each polypide has a more or less elongated cylindrical form, at the 

 distal end of which is fixed a horseshoe-shaped lophophore. For the sake of 

 convenience, the animal may be placed in such a manner that the lophophore 

 comes uppermost, with its convex side directed towtirds the observer, and 

 the various portions of the body may be accordingly denominated as upper, 

 lower, right, left, front, hind, &c. For the last two we may also use the 

 words oral and anal from the position of these openings. As is well known, 

 the cavity of the polypide communicates freely at its lower end with the 

 general cavity of the colony, or the coenoecial cavity of old authors, so that 

 there is only one continuous cavity in each colony. Towards the upper 

 end, the form of the body-cavity becomes somewhat complicated, owing to 

 the presence of certain organs in this region, and also to the peculiar shape 

 of the body itself. 



The exact form and extension of the body-cavity at the upper end of the 

 polypide and its relation with verious organs will be best understood by 

 referring to figs 1-G (PL IX), which show cross sections of the upper portion 



