DAVID B. SLAUTTERBACK 81 



rather spherical in appearance (Fig. 10); they have a very low 

 density content. You can see at the arrows, for instance, a small 

 amount of material within those vesicles. The nematocysts are indi- 

 cated by "Ne"; one in the upper left hand corner and one in the 

 lower right hand corner. It is quite difficult to detemiine exactly 

 which name belongs with which nematocyst. But I would like to 

 say by way of record here, that within one cluster all of the nemato- 

 cysts we have seen are definitely of the same type and they continue 

 to be the same type throughout the stages of differentiation. The 

 relatively homogeneous area is the capsule of the nematocyst, and 

 the granular area will become the tube. Around the open end, 

 where the operculum will finally appear, there is a very dense ag- 

 gregation of smooth vesicles which clearly belong to the Golgi 

 Complex "GC." Notice again, the presence of glycogen granules 

 between cells. 



In Figure 11 there is a cluster of cnidoblasts, early in their 

 differentiation, and you see several sections of nematocysts and 

 the nuclei of these cells. The intercellular bridges are quite conspicu- 

 ous and now the endoplasmic reticulum has become considerably 

 more prominent. The latter is seen mostly as sections of tubular 

 structures, but there is some tendency to form flattened cysternae, 

 typical of such secretory cells as the pancreatic acinar cell, for 

 example. This section, however, has missed the Golgi zones. 

 This particular illustration serves p r i m a r i 1 y to point out the 

 remaining cytoplasmic bridges, and the progressive increase in 

 vesicles of the endoplasmic reticulum. Figure 12 is a higher magni- 

 fication view of cells at a slightly more advanced stage to emphasize 

 the persistence of the intercellular bridges and the continuity of 

 organelles, not simply continuity of cytoplasmic matrix, but or- 

 ganelles seem to be shared between the cells. 



As the nematocyst develops, it acquires the appearance in Fig- 

 ure 13. The Golgi complex is becoming very much more abundant. 

 The centrioles, which are really a diplosome, remain at the open 

 end of the forming capsule. The capsule is the lighter amorphous 

 or faintly fibrous part, and the darker granular material is the 

 forming tube protruding from the open opercular end of the cap- 

 sule. Notice that the Golgi complex forms a close-fitting cap over 

 the growing end of the tube. There is a continuous membrane sur- 



