BERNARD L. STREHLER 385 



cise area in which one would expect it (see Fig. 11). The enzymes 

 (and lysosomes?) are locahzed in a pedal disc, although there is 

 some accumulation even in cells that presumably are differentiating 

 into lysosome-containing cells higher on the column. I think this 

 would be interesting to study — the kinds of structures which con- 

 tain the enzyme and whether they are similar to those which are 

 present in other animals. Notice that acid phosphatase occurs both 

 in the gastrodermal and ectodermal layer. 



We were interested to see whether there are changes in the 

 numbers of similar granules in Campanidaria, particularly in the 

 tentacular region where regression starts. In the young hydranth, 

 there is very little acid phosphatase activity. By contrast, there are 

 enormous numbers of very uniformly sized granules in the 10-day- 

 old hydranth as was shown in Figure 8. Note the deposition of acid 

 phosphatase positive material along the cytoplasmic septa separat- 

 ing the gastrodermal cells in the tentacles of a 9-day-old hydranth 

 shown in Figure 12. These cells have huge vacuoles with an om- 

 mentum-like cytoplasmic extension containing the nucleus hanging 



Fig. 11. Accumulation of acid phosphatase-positive granules in the pedal 

 disc of Hydra. Gomori stain. 500X magnification. (From Brock and Strehler, 

 unpublished). 



