83 CLASSIFICATION OF MEDUSA. 



Dalyell, and supported by KoUiker. Dr. Johnston maintained the same view of their nature. 

 Steenstrup struck out a most original and distinct speculation, holding them to be alternate 

 generations, produced by gemmation from a dissimilar parent, and producing eggs from which 

 should spring dissimilar children. 



In all instances where a Medusa has been observed originating from a hydroid polype, 

 the new animal bears the closest resemblance to a naked-eyed Medusa, — a resemblance not 

 merely of external form, but also of internal structure. Indeed, in many cases it would be 

 impossible to draw a line between the two. 



Is it desirable to draw such a line ? Are not the so-called Zoophytes and Medusae animals 

 of the same section ? Discoveries exactly comparable, and still more wonderful, have shown 

 that the higher Medusae themselves afford instances of parallel phenomena. We now know for 

 certain — all the stages of the history having been demonstrated — through the researches of 

 Sars, Dalyell, Siebold, Steenstrup, Price, and Reid, that the ova of the covered-eyed Medusae, 

 belonging to the genera Aurelia, Chrysaora, and Cxjaneea, give rise to polypoid animals, which 

 in their turn originate individual Medusae by fission — or, more properly, as Dr. Carpenter 

 has well suggested, by a peculiar process of gemmation. The higher genera of Discophorce, 

 therefore, are closely linked, anatomically and physiologically, with the Anthozoa hydroida 

 among the polypes. Assuredly any separation of such nearly aUied animals, especially the 

 placing of them in different classes, is exceedingly unnatural. 



In what light are we to regard the relationship between the Medusa and the Polype i The 

 one is not the larva of the other, as often improperly said, because there is no metamorphosis 

 of the one into the other. The first is the parent of the last, and the last of the first, but neither 

 is a stage of an individual's existence destined to begin life as a Medusa and end it a Polype, 

 and vice versa. The notion that the Medusoid of the Campanularia, or Coryne, or Tubularia, 

 fixes itself, and changes into the tjrpical forms of those zoophytic groups, is as inadmissible as 

 the supposition that the hydroid product of the Aurelia is metamorphosed into a Medusa of 

 that genus. Facts show that such is not the case. These facts may be summed, in the 

 abstract, in the following formulae : — 



1st. The case of Tubularia and Campanularia. 



a. The medusoid produces eggs. 

 h. The eggs produce infusoria. 



c. The infusoria fix and become polypidoms. 



d. The polypes of these polypidoms produce medusoids. 



2d. The case of Aurelia, ^c. 



a. The medusa produces eggs. 



b. The eggs produce infusoria. 



c. The infusoria fix and become hydroid polypes. 



d. The hydroid polypes produce medusae by gemmation. 



