86 Charles W . Hargitt. 



some sensory function, it must be more or less evident that such 

 an explanation of the single case cited would hardly hold. 



Nor would it perhaps be more satisfactory to appeal to what has 

 been designated as polarity in explaining either series. The occur- 

 rence of the organs in conjunction with the radial canals and their 

 apparent differentiation from terminal portions of these structures 

 would seem to afford a much more probable explanation of their 

 regeneration at these apparently predetermined positions. And 

 may we not find in this view a simple explanation of the occur- 

 rence of the anomalous case referred to in Figure 4, a, for we 

 find near the margins a more or less complex network of anas- 

 tomosing canals, the presence of one of which may have been 

 the inciting cause of the development of a sensory body at this 

 particular point. 



It is interesting to note in this connection that no appearance 

 of heteromorphism occurred during the entire series of experi- 

 ments. This feature I have referred to in a previous paper, '97. 

 in connection with similar work on Hydromedusae. On the as- 

 sumption that these organs are metamorphosed tentacles we migh 

 naturally look for heteromorphic phenomena similar to that re- 

 corded among the Crustacea, in which occasionally instead of an 

 eye an antenna develops. Nothing of the sort, however, occurred. 

 There seems in every organ and tissue a remarkably inflexible 

 physiological constancy. This is the more remarkable when con- 

 trasted with the highly flexible character of the polyp phase of the 

 group among which are found the widest range and variety of 

 heteromorphism. 



The fact is not overlooked that Rhizostoma is devoid of ten- 

 tacles, which might be assumed as sufficient reason why hetero- 

 morphism of this sort was not manifested. The fact remains, 

 however, that Its polyp has the typical tentacular equipment, and 

 that In Its metomorphism they are resorbed and possibly take 

 the usual course, some of them contributing toward the formation 

 of rhopalia. It might be an Interesting problem to determine 

 in detail just the extent of this supposed metomorphism of the 

 polypal tentacles Into rhopalia. May it not be possible that the 

 supposed metamorphism Is In reality a resorption and that only, 



