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THE BIOLOGY OF HYDRA : 1961 



Toxin Fraction 



Fig. 3. Results of bioassay on groups of 10 ilea pugilator of: (0) whole 

 crude toxin, and various fractions (1, 2, 3, 4) separated by electrophoresis 

 from the crude toxin. Fractions were injected at levels approximating their 

 separate concentration (by weight) in the crude toxin. 



undergoes characteristic hyperplasia beneath that portion of the 

 epidermis containing mature nematocysts. This histological change 

 involves structural polarization, extensive vacuolation of the cyto- 

 plasm, and a change in the staining characteristics and chromatic 

 density of the nucleus (see Fig. 2). The mesoglea separating the 

 hyperplastic gastroderm cells from the nematocyst-containing epi- 

 dermis is also modified. In preparations stained with Mallory's 

 trichrome, the mesoglea shows discrete circular patches which stain 

 differently from the rest of the mesoglea. These patches are always 

 located between hypertrophied gastroderm cells and cnidoblasts 

 in the surface epithelium. 



We have shown the gastrovascular cavity of Physalia to contain 

 and circulate a protein fluid. There is open communication between 

 the gastrovascular cavity and tlie cavity of the battery. It is tempting 

 to speculate that the modified gastrodenn cells basal to the cnido- 



