130 ACALEPIIS IN GENERAL. Part I. 



classifications of Acaleplis the more interesting to the philosopliical student ; and a 

 comparison of these different arrangements may teach ns how to proceed in our 

 attempts to improve the classification of animals generally. 



Though, from the heginning of his brilliant cai-eer, Cuvier had turned his 

 attention to the study of the Acaleplis, and published his anatomy of Rhizostoma 

 long Ijefore the " Regne animal" apjjeared, his "Tableau elementaire," published in 

 1798, contains nothing of importance ujion these animals. It Avas Lamarck who 

 took the lead in their systematic ari-angement. 



CLA.SSIFICATION OF LAMARCK, ISOl and 181 G. 



In liis " Systcme des Aniinaiix sans VcrtMires," pnblislu'd in 1801, Lamarck nnites the Acaleplis 

 and Echinodcrms in one and the same class under the name of Radiaiees, separating them, however, 

 as two distinct orders of that class, as Radiaires Echinodermes and Radicdres Mollasses. The second order, 

 which corresponds to the Acalephs, embraces the following genera : Medusa, Rliizustoma, IJrroe, Lucer- 

 naria, Porpita, Velella, Pliysalia, Thalis, and Physophora. The Ilydroids jiroper are refenid to the 

 class of Polyps. In proposing this arrangement, Lamarck made the first step towards recognizing the 

 natural limits of the class of Acalephs. 



In file " Ilistoire naturelle des Animaux sans Vertebres," published from 181.J to 1822, he adopts the 

 same general elassifieation of tliese animals; but subdivides the Acalephs in the following manner: — 



1st Section. Radiaires Anomales : — 1° Stephanomia. 2° C'estum, Callianira, Beroe, Noctiluca, 

 Luceruaria. o° Physophora, Rhizophysa, Pliysalia, Velella, aii<l Porjuta. 



2d Section. Radiaires Medusaikes : — 1° Eudora, Phorcynia, Carybdea, Avpiorea, C'allirhoe, Dianea. 

 2° Ephyra, Obelia, Cassiopea, Aurelia. Cephea, Cyanea. 



The classification of Lamarck is evidently based upon a mere general appreciation 

 of the relationship of the animals considered by him in detail. Comparative anatomy 

 Avas not yet sufficiently advanced U) fiu'nish definite characteristics of the diflerent 

 groups adopted by the systematic writers of that period. The reunion of the 

 Acalephs and Echinoderms as one class, for instance, is undoul>tedly a great exag- 

 geration of their affinity ; liut it marks, nevertheless, an important progress in 

 the natural history of the lower animals, since such a comljination could only be 

 proposed by one who had already freed liimself. at least partially, from the impression 

 that the presence or alisence of a solid frame was an essential character of these 

 animals, and who began to perceive that the plan of structure, or at least the 

 degrees of complication of that structure, was of higher importance, in a natural 

 classification, than such secondary features. In this connection, it is important to 

 rememljer that Lamarck was one of the naturalists who knew the Echinoderms 

 Ijest, and that he never could have united the Medusa; witli them, had he not 

 perceived the structural relation which forever will unite into one and the same 

 oreat division such animals as Aurelia and Scutella. 



