ClIAP. I. 



HISTORY OF THE ACALEPHS. 



21 



and the works of Cuvier/ Blumeu))afli/ Dumeril,'' Lamarck/ Oken,^ Goldfuss," and 

 Schweigeiy suggest successive improvements in their classification. There remains, 

 however, so much uncertainty respecting the general characteristics of the different 

 groups of Radiates or Zoophytes, that naturalists disagree even as to the classes 

 that should be referred to this type. Cuvier, for instance, unites the Intestinal 

 Avorms and the Infusoria with the Radiates, while DeBlainville refers the first 

 to the Articulata, and the second to his Microzoaires. Cuvier also at first unites 

 the Actiniae with the Acalephs, while he afterwards separates them.* Even the 

 limits l)etween the Radiates and the lower Mollusks are ill-defined, so that Sa- 



^ Cuvier (George), Tableau elciiicntaire de 

 I'Histoire naturelle des animaux, Paris, 1798, 8vo. 

 tig. — Le Regne animal distribue d'apres sou organi- 

 sation, pour servir de base a I'Histoire naturelle 

 des animaux et d'introduction h rAnatomie eomparee, 

 Paris, 1.S17, 4 vols. Svo. tig. 



'' Blumenbach (J. Fk.), Handbueli dcr Natur- 

 geschichte, Gcitting. 1779, 8vo. fig. ; Gotting. 1825 

 (11th ed.), French transl. by Artaud, Manuel 

 d'Histoire Naturelle, Paris, 1803, 2 vols. Svo. fig. 



^ DuJiERiL (A. M. C), Zoologie analyticiue, ou 

 Methode naturelle de Classification des Animaux, 

 Paris, 180n, 8vo. 



* Lamarck (J. B. de), Histoire naturelle des 

 animaux sans vertebres, presentant les caracteres 

 generaux et particuliers de ces animaux, leur dis- 

 tribution, etc., Paris, 1815-1822, 7 vols. 8vo. ; (Sec. 

 edit, augmentee de notes par MM. Deshayes et 

 Milne-Edwards), Paris, 18.35-1843, 10 vols. Svo. 

 — His Cours de Zoologie is also important. 



^ Oken (Lor.), Lehrbuch der Naturgeschichte, 

 "Weimar, 1816, 2 vols. Svo. — Allgemeine Natur- 

 geschichte, Stuttgart, 1833-1842, 14 vols. Svo. fig. 



^ GoLDFUSS (G. A.), Haudbuch der Zoologie, 

 Niirnberg, 1820, 2 vols. Svo. 



' ScinvEiGEE (A. Fr.), Ilandbueh der Natur- 

 geschichte der skelettloscn ungegliederten Thiere, 

 Leipz. 1820, Svo. One of the most valuable text- 

 books of that period. It is full of original obser- 

 vations. 



' At the time Cuvier characterized the Acalephre 

 as a distinct class among Radiata in the first edition 

 of the Regne Animal, published in 1817, the great 



French naturalist included among them the Ac- 

 tinia', now generally referred to the class of Polypi. 

 To this class he liimself removed them in the second 

 edition of that important work. It is a remarkable 

 circumstance, that no advance was made towards 

 a natural classification of the Acalephs from the 

 days of Aristotle to the period when Savigny, 

 Schweiger, Cuvier, and others attempted to improve 

 our knowledge of the lower animals. In the first 

 edition of the Regno Animal we find the same 

 distinction introduced among the Acalephs, between 

 the free and the fixed Acalephs, whicli Aristotle had 

 adojited ; whilst a nundjcr of animals which must 

 be united with the Acalephs are still left among 

 the Polyps, as they were centuries before. From 

 the beginning, then, the class of the Acalephre was 

 far from being circumscribed within natural limits ; 

 and we shall presently see, that it has required 

 the indefatigable investigations of some of the ablest 

 observers for about a century, before the natural 

 afilnities of the animals belonging to this class were 

 fully appreciated. It is one of the most instructive 

 lessons for a student of nature to trace tlie grad- 

 ual progress of the discoveries which have led to 

 the views now prevailing respecting these animals, 

 as they involve discussions upon all the funda- 

 mental ]n-inciples of Zoology. Instead, therefore, 

 of giving only the results of my own studies of 

 the Acalephs, I will attempt, in this work, to trace 

 also this successive growth of our present knowl- 

 edge, with the special view of teaching the young 

 naturalists of America how to proceed in their 

 own reseai'ches. 



