139 



size. Possibly the clefts or lobes of the topmost disc may have 

 been mistaken for tentacles, as they are sometimes very slender 

 and long ; or else there must be in the European species some 

 appendages of a peculiar kind, belonging to the bud, which do 

 not exist in the Boston species. 



According to a suggestion of Dr. T. W. Harris, the transverse 

 divisions of the bud should be considered as indicatino; its pro- 

 gressive growth ; and this view seems to be more in accordance 

 witli the mode of budding in other polyps, than if we consider 

 the divisions as occurring after the bud has arrived at its full size. 



Mr. Desor infers from his observations, that there is no real 

 difference between the development of the common Jelly-fishes 

 {AureJia,) and that of the Oceania and other small Medusae. The 

 law of development is the same for all. They all originate from 

 polyps by budding, and the division which some naturalists have 

 proposed to establish between free Medusse and fixed Medusse 

 proves thus to be without any foundation. It has been suggested 

 that the whole classification of the Medusae must in consequence 

 of these new facts, undergo considerable modification, and most 

 of the Ac ulephcE (at least all the Discophori or Pulmoni grades) 

 should be united with the Hydroidian polyps, as bearing to them a 

 similar relation to that which the butterfly bears to the caterpillar. 

 On the other hand, as the common Hydra is so similar in structure 

 to the polyp state of the common Medusa (Hydra tiiba,) the ques- 

 tion arises as to its real aflinities, since it is not known to undergo 

 any similar process of budding. Is Hydra therefore to be removed 

 entirely from the other Hydroidian polyps^ such as Hydra tuba, 

 Tubularia^ Syncoryne, &;c., or does it undergo some similar pro- 

 cesses which have heretofore escaped the attention of naturalists ? 

 This question will no doubt be soon decided. Meanwhile it ought 

 to be remembered that Sir John Dalyell kept for several years 

 numerous specimens of Hydra tuba under his eyes, before they 

 began to produce Medusce. Mr. Desor himself saw these buds 

 only during a few days, in Boston harbor, and since that time he 

 has not been able to find any.* 



* The observalions^f Mr. Desor on the development of Medusae, give confir- 

 mation to the views already advanced with more or less accuracy by many nat- 

 uralists. ^For a historical summary of the results obtained by different observers, 

 see Dujardin, Annales des Sciences Naturelles, T. IV. p. 257, 1845; and for a 

 general analysis of labors in the same department, see the Lectures on Compar- 



