132 ACALEPIIS IN GENERAL. Part I. 



The peculiar form of tlie diagram of Peron and LcSueur recalls the character 

 of the classifications generally adopted in France at the time of its publication, 

 consisting in dichotomic divisions and subdivisions, providing even for the position 

 of unknown representatives of the methodical framework, and exhibiting more 

 ingenuity than insight into the nature of true classifications. The chief object 

 naturalists had in view in devising such arrangements was rather to facilitate the 

 identification of genera and species, than to ascertain their natural relations. At 

 that time Cuvier had not puldished his views upon classification ; so that the idea 

 of the subordination of characters, so fruitful in important results, did not yet 

 jiervade the systematic -works of the beginning of this century. 



It is much to be regretted, that the very extensive investigati(jns of Peron and 

 LeSueui', and the many admirable drawings of Acalephs made from nature Ijy the 

 latter during his travels in every part of the ■world, should have Ijcen but partially 

 published, and should have remained unknown to most naturalists outside of France. 



CLASSIFICATION OF THE SIPIIONOPIIOK.E BY LESUEUR. 



Lesson, in his " Histoire iiaturelle ik's Zoophj'tes, Acaleplies," lias iiulili>lM.Ml a classification of the 

 Siphonophora; by LcSueur, the orij;inal of which I have been unal)lc to oljtain. LeSueur calls these 

 animals Radiaires mollasses conijioscs, and divides them in the following manner : — 



L<t Group. Isolated: 1° I'orpita and \'elella. 2° Rhizophysa and I'hysalia. 



United: 1° Pliysoi)hora and Stephanomia. 2° Protomedea and Anipinroa. 



From the jdace this paper occupies iu Lesson's account, I am induced to believe tliat it must have 

 lieen drawn up about the time of the publication of the classification of the MedusK proper by Peron 

 and LeSueur. 



Cuvier's influence upon the progress of the natural history of the Acale^ihs is 

 n(jt to ])L' measured by the amount of special information he has contributed to 

 the stock of our knowledge of these anmials, but rather liy the spirit he has 

 infused into the study of Natural History. His recognition of the ibur primary 

 groups of animals, based upon four diflerent plans of structure, not only justified 

 the separtition of the Acalephs as a class, but established at the same time their 

 true relati(m to the Echinoderms and Polyjis in one great natund division : and 

 though Cuvier made the mistake of uniting with them the Ilelmiuths and Infusoria, 

 on account of the simplicity of their structure, he nevertheless disclosed the princi- 

 ple upon which their classification is finally to be settled ; and the mistake he made 

 on that occasion was only the result of his own departure from that very principle, 

 wdien he allowed the consideration of the simplicity of the structure of the Intestinal 

 Worms and of the Infusoria to overrule that of the i)lan of their structure. 



