74 ACALEPIIS IN GENERAL. Part I. 



with more confitlenee, and Avitli a clear uiiderstaiKling i-espectiug tlie true value of 

 the difierences noticed between the animals now referred to it, and also that I 

 may point out the various names under which the diflerent parts of tliese animals 

 have lieen designated )jy different authors in their descriptions. 



It is much to be regretted that no uniform nomenclature has yet been adopted 

 in describing tliese animals. Indeed, there are scarcely two authors, among those 

 who have contributed most to build up our knowledge of the Acalephs, who describe 

 their parts under the same name, and this ever-recurring discrepancy is a serious 

 oljstacle to an easy perusal of their works. This difficulty has arisen from two 

 causes. First, from a diflerence of opinion among investigators respecting the real 

 nature of the parts described, and secondlj', from a laudable desire to avoid ex- 

 jjressing premature opinions upon these structures. Thus, special names were given 

 to any parts in the body of Acalephs that seemed to present characteristic differ- 

 ences, even though these parts might be homological. This conflicting nomenclature 

 has not only made it very difficult to understand the full meaning of the descrip- 

 tions of Acalephs puljlished by difi'erent writers, ]n\t has also led to the impression, 

 that the differences among the different families of this class are far greater than 

 is really the case. Such Acalephs, for instance, as have a certain external resem- 

 blance to Polyps, as the Iljdroids, have lieen described with the terminology 

 generally applied to Polyps ; while the Medusa^ jn'oper have been designated by 

 a nomenclature of their own ; and the Siphonophora) in another way still : the 

 latter, indeed, Ijeing descril)ed in one way liy those naturalists who consider them as 

 single animals, and in another way by those who look upon them as communities 

 of combined individuals. 



To avoid this complication of nomenclature hereafter, I deem it indispeusal)le to 

 consider not only their relations among themselves, but also their relations to the 

 members of the other classes of the same type. Now, surely, if Acalephs are 

 Radiates, they should Ijcar such a structural relation to the Polyps and Echi- 

 noderms, assuming that they belong to the same t\'pe, as the Acephala, Gasteropoda, 

 and Cephalopoda, considered as Mollusks, Ijear to each other ; or the A\^orms, 

 Crustaceans, and Insects considered as Articidates; or the Fishes, Eeptiles, Birds, and 

 Mammals considered as Vertebrates. This is so well understood in our days with 

 reference to the Verteln-ates and Articulates, and in a measure also with reference 

 to the Mollusks, that no naturalist coidd consider it as a progress in his science 

 were a new name introduced to designate the webbed hand of a bat or the 

 flapper of a Cetacean, or the rudimentary extremity of the Lizards with imperfect 

 feet, or any other such serial gradation in tlie development of their different sys- 

 tems of organs. On the contrary, modern naturalists constantly endeavor to 

 simplify the nomenclature of Zoology by tracing the homologies of the most 



