88 THE BIOLOCY OF HYDRA : 1961 



Enchytraeus fmgmcntosus (Fig. 35). This cell is a very active 

 protein secretor and this is the peak of its synthetic activity. It has 

 become completely filled with endoplasmic reticulum plus a few 

 secretory droplets and a very few mitochondria. In Figure 36 I 

 think I can convince you that there are no free ribonucleoprotein 

 granules in this cell; thus, attached RNP granules induce synthesis 

 of protein for export from the cell; whether or not free ones do, I 

 cannot say. 



(I cannot distribute the responsibility for the interpretations 

 presented here, but I would like to acknowledge the important con- 

 tribution of Prof. Don W. Fawcett to this work. ) 



Figures 18, 23 and 15 are reprinted here by courtesy of the 

 Journal of Biophysical and Biochemical Cytology. They appeared 

 in volume 3, page 441 of that Journal. 



The following abbreviations have been used in the accompanying 

 illustrations: 



Centriole — Ce Nucleus — N 



Cnidocil Apparatus — Cn Nuclear Envelope — Np 



Endoplasmic Reticulum — ER Nuclear Pores — Po 



Golgi Complex — GC Nucleolus — No 



Intercellular Bridge — B Operculum — 



Lipid Droplet — L Particulate Glycogen — Gy 



Mitochondrion — M Plasmalemma — P 



Multivesicular Body — MV Ribonucleoprotein Granules — RNP 



Nematocyst — Ne Spindle Fibers — S 



Nematocyst Capsule — C Zymogen Droplet — Z 



Nematocyst Tube — T 



Fig. 1. A pair of interstitial cells showing granular cytoplasm. 8,900X. 

 Fig. 2. Nuclear pores in an interstitial ceil. 10,000X. 



