DAVID B. SLAUTTERBACK 85 



substance of the forming tube, and have now just begun to form 

 the tubular wall and the spines and thorns. So this, I am sorry 

 to say, is the stage soon after the retraction of the tube, which was 

 as you saw before, wound throughout the cytoplasm. And I presume 

 that this retraction is a very rapid process because we have never 

 seen (or recognized) it in progress. On the other hand it may be 

 that some of the tubes which we see lying coiled out in the cyto- 

 plasm having a cross section somewhat thicker than usual, are these 

 tubes undergoing withdrawal. In any case it is clear that there is no 

 visible structure in the tube before it has been withdrawn into the 

 capsule and that all of the intricate structures which appear later on 

 are formed without immediate contact with cytoplasmic organelles 

 and the mechanism of this astonishing feat remains an enigma. 



Figure 25 illustrates some of the elaborate detail of the structure 

 of a stenotele and points out that the endoplasmic reticulum, which 

 has reached a vesicular stage, is now disappearing and that the 

 phospholipids of that membrane have gone some place else. It 

 might be interesting to follow the displacement of these phospho- 

 lipids with histochemical procedures, but we have not as yet tried 

 such things. 



The isorhiza in Figure 26 illustrates a similar course of events 

 in that type of nematocyst: the endoplasmic reticulum has become 

 vesicular and vanished to a very large degree. The coiled tube is in- 

 dicated at "T," and I presume that this is a holotrichous isorhiza be- 

 cause, in some areas (arrows), we see what appear to be develop- 

 ing thorns. At "Cn" in the upper right of the figure is the region 

 where before we saw the diplosome and now we see what Hyman 

 has referred to as the stiff rods which surround the operculum, a 

 part of the cnidocil appartus. 



A similar degree of differentiation is seen in Figure 27, but the 

 section has passed through the operculum and the cnidocil. One 

 of the centroiles of the basal granule is at the base of the cilium, 

 which, I believe, is just in the process of forming, and is quite broad 

 in diameter. And just outside it, you can see one of the stiff rods. 

 Now this is not the dense part, which you saw in the section im- 

 mediately preceding, but this is the part which corresponds to the 

 body of the cilium itself. The endoplasmic reticulum is much dimin- 

 ished. The Golgi complex has retreated to the basal area of the cell 



