140 I. IJIMA : HEXACTINELLIDA. I. 



owing to shrinkage caused by tlie action of the reagents. I think 

 it is approximately cylindrical in the natural state. In the 

 preparations that shape is sometimes retained ; but more frequently 

 the collar either gradually narrows toward the distal end or is 

 somewhat narrowed in the middle section, in ^vhich latter case 

 the distal end is often expanded in a funnel-like manner. The 

 flagellum traverses the collar either at its middle throughout or 

 along one of its lateral edges after having inclined to that side 

 at a certain distance away from the origin of the flagellum in 

 the center of the distal nuclear surface. In height the collar 

 measures 0-6 /i (0.6 ,« on an average). The breadth usually 

 measures only V/o-2 ,n (1.7/^ on an average), i.e., about as much 

 as the diameter of the nucleus. It may however occasionally 

 reach 3 ,« at the base or at the expanded distal end of the collar. 

 In one or two instances I have seen a line apparently 

 stretching itself between and connecting the flaring rims of a 

 few consecutive collars, which line reminded me at once of SoUas' 

 membrane. But I have satisfied myself that it is to be regarded 

 as something accidentally produced, — possibly a flagellum or 

 portions of flagella laid down upon the free ends of the collars. 

 The collars stand out freely and solitarily, being separated from 

 one another by a comjjaratively wide space whose width may be 

 said to be on the whole about equal to the distance between the 

 nuclei of the respective choanocytes. 



Observations of the chamber-wall in the fresh state, 2-5 hours 

 after the capture of the specimens, did not reveal anything of 

 much importance. The preparation of a piece of the fresh 

 choanosorae for examination under the microscope necessarily 

 involves more or less dislocation of spicules from their proper 



