398 THE BIOLOGY OF HYDRA : 1961 



upright and produced a new little liydranth, Figure IE. Presumably 

 all of the new growth is made possible by utilizing the debris of 

 the regressing hydranth and just a small quantity of good, new cells 

 which at first were assembled at the base of the isolated hydranth. 

 If so, this experiment of Nathanson points to a very rapid utilization 

 and reorganization of this stuff in the building of new cells. No one 

 has looked at such preparations with anything more powerful than 

 a binocular microscope. This looks like a good place to make a 

 start on the problem. 



CHAPMAN: Do I understand you to indicate that you thought 

 the dense particles in your electron micrographs indicated by the 

 arrows were lysosome particles? 



STREHLER: Possibly. 



CHAPMAN: If you thought they were, I want to tell you I thought 

 they weren't for two reasons. One, it seems to me they are too large 

 to be lysosomes. Lysosomes fall in the range between the smallest 

 mitochondria and the largest elements of the so-called microsome 

 fraction. And two, they looked almost homogeneous to me and I 

 would expect a more dense outer shell. 



STREHLER: I think you are in error because lysosomes are quite 

 variable in size. If you look at Essner and Novikoff's electron 

 photomicrographs of liver lysosomes, the size variation occurs and 

 they frequently appear with a moon shaped heavy border. This 

 looks like a vesicle in this micrograph. But the acid phosphatase ac- 

 tivity is actually usually associated with the dense staining portion. 

 I don't think there is really enough structure in those particles to 

 answer the question. 



