118 



ACALEPIIS IN GENERAL. 



Part I. 



nostome are so for distinct from tlie main cavity, that they only communicate with it 

 through the channels extending along the centre of these folds ; "while in the naked- 

 eyed Medusa; the actinostome opens liroadly into the main cavity. The chymiferous 

 tubes arise from the upper part of the sides of the main cavity. 



It thus appears that the Discophora^ proper have a far more complicated strvict- 

 ure than the naked-eyed Medusa?, and that, in a natural classification, they cannot 

 therefore lie united into one and the same order, as has thus far been done by 

 most naturalists. Moreover, the Discophoraj resemble one another very much in 

 their general appearance and in their motions, which are eflfected by a slow alternate 

 expansion and contraction of the disc. 



The Hydroids, as the lowest order of the class of Acalephs, are far more 

 diversified among themselves than either the Ctenophora" or Discophora^.^ In the 

 first place we find among them simple Hydroids, in the next j^lace more or less 

 medusoid Hydroids, then commiurities of variously coml^ined individuals Avith more 

 or less medusoid or hydroid charactei's ; and among these communities there are 



' It is a striking fact, cunflicting with all pre- 

 conceived ideas, that throughout the animal king- 

 dom, the lower types, in every class, are far more 

 diversified than their higher representatives. It is 

 so among Polyps, if the Actinoids are inferior to 

 the Halcyonoids ; it is so again among the Aetinoids, 

 if the Madrepores are the highest among them. It 

 is so among the Acalephs, if the Ctenophorre are 

 the highest and the Hydroids the lowest. It is 

 so among Echinoderms, if the Holothurians stand 

 highest and the Crinoids lowest. It is so among 

 Aeephala, if the Bryozoa belong to that class. It 

 is so amiing Gasteroi)ods, if tlie Pulmonates are 

 superior to the Branehiates. It is so among Cepha- 

 lopods, if the Dibranchiates deserve to be placed 

 above the Tetrabranchiates. It is so among Worms, 

 if the Helminths belong to the same class with 

 the Annelids. It is so among Crustacea, if Rotifera 

 and Entomostraia are their lowest representatives. 

 It is so among Insects, if the Myriapods and Arach- 

 nids are united into one class with the Insects 

 proper; and it wouhl still be so if the winged 

 Insects were considered as a class by themselves, 

 for the madibulate Insects are more numerous and 

 more diversified than the sucking Insects, and those 

 which undergo the most complete metamorphoses 



fewer and less diversified than those whose meta- 

 morphoses are less complete. It is so among 

 Fishes, if the bony Fishes are inferior to the Se- 

 lachians. It is so among Amphibians, if the caudate 

 Amphibians are inferior to the Frogs and Toads. 

 It is so among Eeptiles proper, if the Chelouians 

 deserve the highest, and the Ophidians the lowest, 

 ])l;ice in that class. It is so among Birds, if the 

 Palmipeds are their lowest representatives. It is 

 so among Mammalia, if we contrast the Marsupials 

 with the higher Mammalia ; or if among the latter, 

 we compare the Rodents with the Human family. 

 Of course, this greater diversity does not involve 

 respectively greater differences among the lower 

 representatives of any class when compared to one 

 another, than among the highest ; since their very 

 inferiority, combined with great diversity, renders 

 the jjossible amount of dift'erence among the many 

 lower ones less than among the fe^ver more highly 

 organized ones. This very extraordinary diversity 

 among the lowest types of all the classes of the 

 animal kingdom stands in flagrant contradiction 

 with Darwin's theory of the origin of species, 

 according to which the lowest types should grad- 

 ually give way to higher and higher types, in 

 consequence of the struggle for life. 



