CHARLES E. LANE 175 



blasts absorb precursor materials from the circulating gastrovascular 

 fluid and from these synthesize the toxin which they subsequently 

 secrete through the mesoglea and into the cnidoblasts. 



Slautterback and Fawcett have shown that the nematocyst thread 

 in hydra originates from outside the nematocyst capsule and is 

 subsequently introduced into the cavity of the nematocyst. If a 

 structural component of the nematocyst may be formed external 

 to the nematocyst capsule and subsequently introduced into it, it 

 should not stretch our credulity too far to accept the suggestion 

 that a soluble protein toxin may be synthesized outside the nema- 

 tocyst and later may pass through it. One disturbing observation 

 is that this would suggest or almost require that the nematocyst 

 capsule be permeable to the toxin. We have repeatedly observed 

 that the toxin does not leach from surviving purified nematocysts. 

 Presumably, therefore, there is one stage in the morphogenetic 

 history of the nematocyst when the capsule wall may be permeable 

 to toxin but in the mature nematocyst these permeability relation- 

 ships may be completely changed. 



I suggest that Phijsalia toxin is synthesized by gastrodermal 

 cells, passes through the mesoglea, and into the nematocyst during 

 the morphogenesis of this structure. 



DISCUSSION 



CROWELL: Where are the nematocysts manufactured in Phijsa- 

 lia? Where is the differentiation of the cnidoblasts taking place? 



LANE: I can't answer because I don't know yet. I can tell you 

 a few of the things we do know. In adult animals the float is 

 generally free of cnidoblasts. The basal ends of gastrozoids are 

 deficient in cnidoblasts. Cnidoblasts appear to be reasonably uni- 

 formly distributed throughout the length of the fishing tentacle. I 

 have seen no clear histological evidence of interstitial cells such 

 as we have heard about in hydra. Obviously they must be there, 

 but I haven't seen them. 



CROWELL: Is it possible that the whole tentacle is continuously 

 growing so that it's always young basally and degenerating api- 



