352 ASAJIRO OKA; ON THE SO-CALLED 



where the latter is thickened and ciliated. Where such modification 

 takes place is indicated by thickening of the line and by putting fine 

 oblique lines on it. The arrows show the communications between 

 various cavities in the neighbourhood of the organ. 



As stated above, my researches lead me to conclude that the 

 statements in my former paper with regard to the connection of the 

 median tentacles with the ciliated tubes are correct. In his second 

 paper, CoRi criticises my observations on this point in the following 

 words ; " Es dürfte auch in diesem Falle ein Untersuchungsfehler, 

 was die Verbindung des genannten Organs mit den Tentakeln betrifft, 

 vorliegen, wie auch in Bezug auf das Fehlen der äusseren Öffnung." 

 I am ready to acknowledge the correctness of this remark as far as 

 concerns the presence of the external opening, but as to the first part 

 it is difficult for me to accept its validity. The figures in Coiti's own 

 paper, especially the figures 6-10, can not be interpreted as showing 

 the continuity of the tentacular lumina with the lophophoral cavity 

 outside the ciliated tubes. It is however no easy task to observe the 

 true bearings of these cavities, for in the majority of individuals, the 

 floating cells or the leucocytes, of which I shall speak afterwards, are 

 accumulated in masses at the base of the tentacles, making the com- 

 munication of the latter with the ciliated tubes extremely obscure. 

 And it was no doubt this circumstance that caused the difference in 

 our statements. 



As to the histological structure of these tubes I have nothing new 

 to add. In the paper referred to above, Cori describes and figures 

 the cells that constitute various parts of the organ : " Von dem 

 Leibesepithel hebt sich das Trichterepithel deutlich durch die Hellis;'- 

 keit seines Plasmas ab. An der freien Fläche zeigen ferner die mit 

 langen Wimperhaaren versehenen Trichterzellen einen äusserst scharfen 

 Kontour, der entsprechend die einzelnen Zellen kleinen Unterbrechiin- 



