E. MAESIIALLT. — FLAOELLATED CHAMBER, 145 



surface of the basall y situated nucleus to the origin of the flagel- 

 lutn at the terminal surface of the collum-like section. 



Now the choanocyte of E. marshalli, as I have described it, 

 lacks the collum-like middle section. It has been described as 

 consisting only of a collar and of a flattened body, which at any 

 rate partially corresponds with the base of the choanocytes in 

 Schulze's sense (1 si\y 'partially, merely because I do not assume 

 the presence of a web-like closing membrane between the lateral 

 processes or reticular beams). 



In attempting to reconcile the above difference in our stand- 

 points, the following possibilities suggest themselves : 1) The 

 collum-liJce section may he something that really is entirely wanting 

 in E. marshalli. In view of the general uniformity of histolo- 

 gical structure throughout the entire group, the assumption of 

 such a marked variation seems to be scarcely warranted. And 

 yet, a considerable range of variation, so far as the size of the 

 choanocytes is concerned, is to be admitted ; for, Schulze has 

 given for the total height of choanocytes in S. arctica 10-12//, 

 and for the greatest breadth o.Q « ; against which dimensions, the 

 size of the same in E. marshalli as found by me is only about one- 

 half as large or even smaller. 2) The part lohich I have taken 

 solely for the collar may include the collum-lihe section of the 

 cell-body. The narrow shape of that part seems to lend color to 

 this possibility. However, I have never detected the slightest 

 difference in the appearance of the basal and distal parts of the 

 structure in question. It is uniformly and homogeneously trans- 

 parent throughout. 3) / may h.ave seen only the collum-lihe sec- 

 tion, but not the true collar. I must declare myself against this, 

 as well as against the preceding, assumption, on the ground that 

 the flagellum is frequently seen to bend in one way or the other 



