84 THE BIOLOGY OF HYDRA : 1961 



tion of the nematocyst, the Golgi complex is at all times in close 

 proximity to the tip of the forming tube and that tube is formed 

 out in the cytoplasm. It may become very very long and coiled 

 around through the cytoplasm, but the Golgi complex caps the 

 growing tip. 



In Figure 21 is a cnidoblast which has passed its peak of syn- 

 thetic activity. We considered for sometime that the expansion 

 of these endoplasmic reticulum vesicles was a fixation artifact due to 

 osmotic differences in the fixative as compared to those within the 

 cell. But by using a very wide variety of osmotic strengths and 

 hydrogen ion concentrations, we have convinced ourselves that 

 this is exactly what happens to the reticulum after it has passed 

 the peak of synthetic activity. It begins to swell up, perhaps with 

 an acute hydration of its contents. I wouldn't like to extend myself 

 on that point, but in any case they do become vesicular again. 



In Figure 22 you will see a nematocyst, which shows how this 

 forming tubule continues around through the cytoplasm. The ab- 

 sence of Golgi vesicles from this section clearly indicates that there 

 are still more coils of tubule elsewhere in this cell for if the tip were 

 here we would see the Golgi membranes surrounding it. 



The cell in Figure 23 shows a still more advanced condition 

 and this one is an early stenotele. The Golgi membrane sur- 

 rounding the nematocyst is clearly discernable, and now we begin to 

 see a concentration or aggregation of dense granules which were 

 once randomly distributed. It is in this zone that the spines and 

 thorns of the nematocyst tube will be formed. In this micrograph 

 there are four sections through the coiled tube which is still outside 

 of the nematocyst capsule. The darker bodies are mitochondria, and 

 the endoplasmic reticulum is clearly vesicular and considerably de- 

 creased in amount indicating the end of the synthetic phase. Though 

 not present in this illustration, the Golgi complex is still active evi- 

 dently collecting and concentrating material synthesized earlier in 

 the now regressing reticulum. 



A more advanced stenotele cut longitudinaly is seen in Figure 

 24. The tubule has been withdrawn and the open end of the 

 capsule is closed by the operculum. The laminated structure of the 

 operculum can be seen in Figure 31. The arrows point to the ele- 

 ments which were originally distributed at random throughout the 



