Chap. I. ADULT MEDUSA OF CORYNE MIRABILIS. 217 



This case of Medusa, with different numbers of rays is precisely parallel to 

 the case of Star-fishes with a variable number of rays, such as have been described 

 by the older Linck, who, unfortunately for himself and the progress of science 

 considered each variation, in this respect, as indicating generic distinctions ; when 

 he might easily have ascertained that several species vary greatly in this respect 

 Since the genus Sarsia was first characterized by Lesson, several species have 

 been added to it by Forbes, Busch, and McCrady ; but I do not believe that these 

 all belong to the genus Sarsia, and not even to the same family. The proliferous 

 species described by Forbes and Busch, and the Sarsia turricula McCr., resemble 

 much more the free medusa, of certain Tubulari* described in the sequel than 

 the true Sarsia. arising from Syncoryne, and must, therefore, be referred to that 

 hxmily, to which, as we shall hereafter see, the genera Steenstrupia and Euphyra also 

 belong. Oceania thelostyla Geyenh., on the other hand, belongs to a distinct genus 

 lately characterized from a species discovered by my son on the coast of Massa- 

 chusetts. This genus is closely allied to Sarsia, both in its hydroid and medusoid 

 generation. Thus far it might have appeared that the genus Sarsia was confined 

 to the two sides of the Atlantic Ocean, within the limits of the northern temperate 

 zone; but, during his residence upon the Pacific coast of North America, my son 

 has observed a genuine Sarsia, closely allied to the European S. tubulosa, the 

 development of which, from a Syncoryne, he has also traced. This fact is of the 

 highest importance, as showing that Medusa, which are generically identical, arise 

 from Hydroids bearing identical generic relations. 



vol.. IV. 



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