Chap. I. HISTORY OF THE ACALEPHS. 10 



the edifice. Thus far all the Discophora^, -whether covered-eyed or naked-eyed, had 

 been placed in one and the same genus, and even the Ctenophora^ were associated 

 Avith them. Only a few species of SiphonophortB were referred to other genera : 

 ])nt then these were not placed in close proximity with the Medusie proper, and 

 the Hydroids were unhesitatingly referred to the class of Polyps, or at least arranged 

 among them. The whole number of genera distinguished among the animals now 

 referred to the class of Acalephs amounted only to thirteen in 1801 ; namely, Beroc 

 Bro/m, Medusa L., Physalia Laiurl: (first called Arethusa by P. Brown, then Physalis 

 by Osbeck and Salacia Ijy Linnanis), Velella LamrJc, and Porpita LamrJc. (first called 

 Phyllodoce and Thalia by P. Brown), Gleba Bniy., Physophora Forslc, Lucernaria 

 3IUU., Hjdra L., Coryno (lariii., Tuliularia Z., Sertularia LamrJc, Millepora L. 



Owing to the greater number of Medusae now known, including species from 

 distant parts of the world, and also to the discovery of numerous animals more 

 or less closely allied to them, it has become necessary to institute comparisons 

 between the animals of this class and the representatives of other classes, wdiich 

 were not even suggested Ijcfore. This is therefore truly the age of Comi^arative 

 Natural History ; and a new science, Comparative Anatomy, arises with it, by the 

 irig;antic labors of the scientific hero of modern times. 



Peron and LeSueur ^ open this period with investigations upon a far greater 

 number of species of Acalephs than had been olaserved Ijy all the investigators of 

 former ages taken together. Engaged as naturalists in the expedition of Captain 

 Baudin to the South Seas during the first four years of this century, they had 

 the fullest opportunities of examining these annuals alive ; and LeSueur, with incom- 

 parable skill, reproduced their delicate appearance in a series of colored plates, so 

 magnificent and of such costly execution, that to this day a small part of them 

 only have been published. But these illustrations Avere dejiosited in the liln-ary 

 of the Jardin des Plantes in Paris, and have been extensively used by French 

 naturalists who have written upon Acalephs during the last thirty years. The}' 

 are referred to, and partly copied b}', de Blainville in his Manuel d'Actinologie. 



^ Peron (Fr.) et LeSueur (C. A.), Voyage two [wpers relating to the Acalephs and allied anl- 



de decouvertcs aux Terres Australes, pendant les mals : Menioire snr qnelipies nouvelles especes 



anuees 1800-1804, Paris, 1807-1816, 3 vols. 4to. fig. d'Animaux Mollusiines and Radiaires recueillies dans 



— Histoire generale et partieuliero de tons les Ani- la Mediterranee pres de Nice, Jonrnal de Pliysiqnc. 



maux qui composent la famille des Meduses, Ann. vol. 77, p. Ill), and Memoire sur I'organisation des 



Mus. XIV. p. 218. — Tableau des Caracteres gene- Pyrosomes et sur la place qu'ils doivent occuper 



riques et specifiques de toutes les especes de dans une classification naturelle, Journal de PI13'- 



Meduses connues jusqu'ii ce jour. Ann. Mus. XIV. sique, vol. 80, p. 41.3. He was the first to suggest 



p. 32.5. — Sur les Meduses du genre Equoree, Ann. that the Siphonophoraj are compound animals, — an 



Mus. XV. p. 41. — LeSueur by himself published opinion now almost universally admitted. 



