OF CONCHOLOGY. 



123 



Geoffroy St. Hillaire, that his sneering satire was directed. This 

 doctrine has now, chiefly through the hibors of Prof. Owen, be- 

 come universally adopted as one of the main principles of 

 natural science. Perhaps the comparison of analogical species 

 of different groups will some day take the same rank in the 

 science. 



On the emhryological systems. 



Redi and Schwammerdam founded, in 1669, a system for the 

 lower animals according to their development, (chiefly of the 

 Insects.) It was only in this century that the development of 

 the marine animals became sufficiently known that it could serve 

 as a base for a system. 



M. Edwards,* Owen and YanBeneden, considered the develop- 

 ment of an animal to indicate its place in the system, and that 

 the various forms represented the different stages of foetal de- 

 velopment. Later discoveries have, however, shown that animals 

 nearly of the same genus have different modes of development, 

 for instance Astacus, Homarus, Asteridae. The development 

 proves only relative superiority and inferiority between animals 

 of the same group and living under the same circumstances, but 

 not the limits of higher systematic divisions. Marsupialia and 

 Amphibia are very natural groups, although many of the former 

 want the pouch, and the development of the young of the latter 

 group is rather variable. Prof. Danaf has lately based a new 

 classification on the different arrangement of the locomotive 

 organs and introduced a corresponding nomenclature which may 

 prove of great use if applied to Prreordines or to Subclasses, but 

 not to higher divisions. Thus, Neuroptera are removed from 

 Orthoptera to Pteroprosthenica (Lepidoptera, Hymenoptera) 

 whilst Hemiptera are associated with Orthoptera and Coleoptera 

 in the group Pterometasthenica, notwithstanding their oral parts ! 



On the guiding laws of zoological classification. 



The principal aim of taxonomy is to decide the rank and rela- 

 tive relations of the various systematic divisions. These relations 

 are generally determined entirely arbitrarily, without reference 

 to zoology in general ; chiefly because most naturalists content 

 themselves with studying single groups without comparison of 

 the alterations and reciprocal relations of the organs throughout 

 extensive suites. Great vitality or special development of a 

 single organ are frequently erroneously considered characters of 

 superiority chiefly among the lower animals, although a com 



* An. Sc. Nat., 3 Ser. t. 2, 1844, p. 162. Owen Lectures, 1813. 

 tThe American Journal of Science and Arts, ix. p. 369. 



