82 THE BIOLOGY OF HYDRA : 1961 



rounding this forming nematocyst which is agranular, and in all 

 respects resembles that of the Golgi complex. You will see that the 

 Golgi complex is formed as usual in vertebrates of flattened vesicles, 

 expanded vesicles, and small spherical ones. It has been said that 

 such appearances are not common in invertebrates and represent 

 more of a vertebrate type of Golgi complex, so then hydra cnido- 

 blasts have a vertebrate type of Golgi complex, if that's the case. 

 The large body here at the top of the figure is lipid droplet, and in 

 our experience lipid droplets are a ubiquitous finding in all secretory 

 cells. Of course, lipid droplets are found in virtually all cell types, 

 but a relatively sudden accumulation of lipid seems to go hand in 

 hand with the differentiation of these secretory cells. 



In another section of the opercular end of a developing nemato- 

 cyst ( Fig. 14 ) the Golgi membranes surrounding the growing tubule 

 can be seen more clearly. In the Golgi zone, the three types of 

 vesicles are evident and especially prominent in this micrograph, 

 is this large expanded one (indicated by an arrow) whose 

 contents appear every similar to those of the nematocyst capsule. 

 The only appreciable difference seems to be a slightly greater den- 

 sity of the material in the nematocyst than in the Golgi vesicle. 

 One can often see areas where these Golgi vesicles seem to increase 

 gradually in size getting larger and larger, and finally one of the 

 vesicles seems to join by fusion of its membrane with that of the 

 membrane surrounding the nematocyst tube or rod. This process 

 is illustrated in Figure 15. It bears a remarkable resemblance to the 

 mode of release of secretory granules in other cells in which the Gol- 

 gi membrane surrounding the granule fuses with the plasmalemma 

 and the membrane is broken at the point of fusion releasing the 

 secretory product and adding the Golgi membrane to the plasma- 

 lemma. As you can see the endoplasmic reticulum is continuing to 

 develop. We are not yet past the peak of protein synthesis in this 

 cell. That similar configurations are present in the isorhizas is 

 evident from Figure 16. Here a large Golgi vesicle is being added 

 to the nematocyst tube. Though some degree of uncertainty re- 

 mains as to the identity of these developing nematocysts, those 

 which you have seen before were probably desmosomes, but this 

 one is an isorhiza, though whether it should be regarded as holo- 

 trichous or atrichous, I cannot say. But again, you see the cen- 



