48 THE BIOLOGY OF HYDRA : 1961 



such bridge between any two cells in the cnidoblast cluster. The 

 bridges persist throughout the period of differentiation of the nema- 

 tocysts. If the nematocysts are eventually to migrate as individual 

 cells, the bridges connecting them must be severed at some time 

 late in their differentiation, but this process has not yet been ob- 

 served. We believe that the syncytial relationship of the cnidoblasts 

 is probably the morphological basis for the synchrony of their differ- 

 entiation. It is interesting that the same kind of synchrony is seen 

 in the groups of developing germ cells in the testes and these are 

 also connected by intercellular bridges that form in the same way. 



CLAYBROOK: Do either of you find cytoplasmic bridges between 

 different cell types, or are they only between two of the same kind? 



HESS: I've only seen them between the same cell type. How about 

 you? 



FAWCETT: Bridges of the kind I have been describing occur only 

 between cells of the same type. 



HESS: I've seen a break in the cell membranes of the spermatids, 

 like the first type of interconnection of which you spoke. We 

 thought that it was an artifact until we saw cytoplasm and mito- 

 chondria in the intercellular bridge running between the two syncy- 

 tial cells. 



GAUTHIER: May we return to the subject of gland cells? If the 

 two cell types represent only a cyclical change in one cell type, 

 would you expect that starvation might produce a levelling off so 

 that only one type would be present? 



HESS: Well, I thought that the different appearances of gland cells 

 indicated cyclical changes of one cell type, but others here appar- 

 ently disagree. 



GAUTHIER: In preliminary experiments with starved hydra, I 

 have found that two distinct types of gland cells persist for as long 

 as twelve days, 



GOREAU: I am interested in the so-called microvilli you have 

 shown. We have seen microvilli in gorgonian and scleractinian 

 material which have a much more regular and permanent appear- 



