354 ASAJIRO OKA; ON THE SO-CALLED 



For marine Polyzoa S. Harmer (1892) proved the excretory 

 activity of the leucocytes as well as other cells of the body, by keeping 

 living colonies in sea-wjiter holding the fine powder of various insoluble 

 colouring matters in suspension. After doing so for a short time he 

 found that the fine grains were greedily devoured by the leucocytes. 

 CoRi, who carried on similar experiments with CristateUa, observed 

 that the same was the c;ise with Phylactolaematous Polyzoa. More- 

 over he found that cells charged with excretory substance ^^ere fi'om 

 time to time expelled through the external pore of the ciliated tubes. 

 It is thus certain that the true excretory ])art in Polyzoa is repre- 

 sented by the floating cells or leucocytes, as Kowalevsky pi-oved by 

 his beautiful experiments with certain worms. 



Although 1 have not seen actually a polypide discharging the 

 leucocytes, a careful examination of these cells, especially those ac- 

 cumulated in the ciliated tubes, convinces me of the very high pro- 

 bability of the above phenomenon occurring in FectinateUa. If we take 

 a living colony and observe it under the microscope, we find a great 

 number of round or oval cells circulating in the body in a pretty rapid 

 stream. Some of them, which I compared erroneously with blood- 

 corpuscles of other animals in my former paper (1890), are tilled up with 

 a vacuole containing a liquid of a pale yellowish colour. Others, again, 

 show a few vacuoles of smaller dimensions or a large number of minute 

 ones. In stained preparations, tliey look much like the figures given 

 by CoRi. In sections I found them most abundant in the epistomal 

 cavity or along the great retractor muscles. In most of them the nuclei 

 bear signs of degeneration, the chromatic substance being sometimes 

 melted together to form a conspicuous deeply-staining b;ill. As such 

 cells are always found accunuilated in the unitubular portion of the 

 ciliated canals, I am inclined to believe that they are thrown out, toge- 

 ther with the excretory substance held b}^ them, in the manner described 



