VARIATION AMONG HYDROMEDUSAE. 



CHAS. W. HARGITT. 



THE announcement of Bateson ('94), that " in the whole range 

 of natural history there is no more striking case of the dis- 

 continuity and perfection of meristic variation than in the 

 genus Sarsia, and the further proposition whether it is a mere 

 coincidence that the specimens presenting this variation, so 

 rare among the free-swimming Hydromedusae, should have 

 been members of the same genus," directed my attention to 

 this particular problem in conjunction with work upon this 

 group of coelenterates which had engaged my attention for 

 several years. 



During the following years, therefore, collections of free 

 medusae of several genera were made with a view to testing 

 the problem raised by this observer. While as yet these col- 

 lections are not extensive, except in a few genera, certain facts 

 have been secured which may not be without value in their 

 general bearing upon this as well as still broader problems of 

 variation in general. 



My collections have been restricted chiefly to the genera 

 Eucope, Obelia, Margelis, Pennafia, Gonionemus, Coryne 

 (Sarsia), and Hybocodon ; the specimens of several others 

 have been casually examined. Of the genera named, Obelia 

 has not as yet been examined in sufficient numbers and detail 

 to warrant any specific mention in this connection. And since 

 these observations have been under way a paper by Agassiz 

 and Woodworth ('96) on " Some Variations in the Genus 

 Eucope" has appeared which so fully covers the facts involved 

 in members of that genus, and are so coincident with my own, 

 that no special details will be offered in connection with it, 

 though the materials at hand are more abundant than upon 

 any of the others. 



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