190 THE BIOLOGY OF HYDRA : 1961 



amastigophores (microbasic and macrobasic amastigophores of 

 Weill). Ciitress also made a number of claims about nematocysts, 

 some of which are wrong and others certainly are questionable. 

 Unfortunately we have not yet progressed far enough in our study 

 to analyze critically all of the structural details of all nematocysts, 

 and until electron microscope studies have been extended to many 

 more types of nematocysts, a number of suggestions Cutress has 

 made cannot be proven or disproven. 



One of Cutress' suggestions is that the shaft or butt of mastigo- 

 phores is folded within itself as well as being inverted before ex- 

 plosion. This would bring the point of the butt to the tip of the cap- 

 sule, would keep the point in the lead as the basal half of the butt 

 everts, and he claims the thread is attached to this leading tip of the 

 shaft. The tread would evert after the shaft has completely emerged. 

 Miss Jane Westfall of the Department of Zoology at the University 

 of California at Berkeley has been examining a number of nemato- 

 cyst types with the electron microscope and has been particularly 

 interested in mastigophores. Her studies have not yet progressed to 

 a point where publication seems warranted, but we can comment 

 on Cutress' suggestion. Both cross and longitudinal thin sections 

 have been examined as well as whole exploded nematocysts. The 

 material has been primarily the nematocysts of the acontia of our 

 West Coast Metridiiim senile fimbriatum. Cross sections of micro- 

 basic amastigophores, microbasic b-mastigophores and basitrichs 

 (sensu Weill and Carlgren, refs. 2, 10) show clearly that the shaft 

 is not folded on itself and contains only the spines. The spines are 

 blades, as was shown so clearly by Robson (8), and are oriented 

 with their tips toward the open end of the capsule. Longitudinal 

 sections of amastigophores also show that the notch seen in the 

 light microscope at the distal end of the shaft of amastigophores and 

 p-mastigophores is the result of this being the end of the armored 

 region of the shaft. Moreover, there is no thread within the shaft 

 as Cutress has proposed. From these observations we conclude that 

 Cutress is wrong, as were certain earlier workers who proposed 

 folded as well as inverted shafts. It also should be noted that from 

 the work of Picken ( 7 ) and Robson ( 8 ) that Cutress' claim that the 

 holotrichs of Corynactis, which he calls macrobasic p-mastigo- 

 phores, has an inverted and folded shaft is wrong. 



