REPORT ON ZOOLOGY. 231 



tomostraca, to which they are referred by Blain ville, Straus-Durck- 

 heim, Edwards, and others, although placed by Cuvier at the end 

 of his Intestinaux Cavitaires. Blainville has made a particular 

 study of this family, in which he has characterized eight distinct 

 genera*. Nevertheless, we stand much in need of further informa- 

 tion respectingtheir structure andoeconomyf. On tlie other hand, 

 the Acephalocysti, and the Hydatids in general, appear so low in 

 the scale of organization, that it may be questioned whether 

 they can be placed in the same class with all the other groups 

 included in Cuvier's second order. Nitzsch and Leuckart, as 

 well as Dugez, think that the Acephalocysti are allied to 

 the F'olvoces diwd other vesicular /«/M5or?'a J. M. Kuhn, in a me- 

 moir lately published §, does not consider them as true animals, 

 but thinks that they should have a place assigned them amongst 

 those ambiguous beings which hold a middle rank between the 

 animal and vegetable kingdoms, and to which Bory St. Vincent 

 has given the name of Psychodiaires. 



From the above observations it will be seen how much re- 

 mains yet to be done towards a natural arrangement of these 

 animals. Those who would enter into the details of their history, 

 will do well to consult, — besides the memoirs already alluded to, 

 and the works of Rudolphi, which are well known, — the works 

 of Bremser||, Cloquet^, Creplin**, and Leuckartft- Bremser, in 



* SeeJourn. dePhys. (1822), torn. xcv. pp. 372 and 437; also the 26tli vol. 

 of the Diet, des Set. Nat., art. Lerne'e. 



f According to the observations of Dr. Surrirey of Havre, the LerncecB un- 

 dergo a metamorphosis, and are very diflei'ent in their young state from what 

 they are in their adult. (See Blainville ml)ict. des Sci. Nat., torn. xxvi. p. 115.) 

 Since this Report was read, I have learned that the above fact has been recently 

 confirmed by M. Nordmann, who is said to have published several very inter- 

 esting researches connected with the gradual development of these animals, and 

 8uch as leave no doubt of their forming part of the same group with the Sipho- 

 nostomous Crustacea. These observations are contained in a work entitled, 

 " Mikrographische Beitrage zur Naiurgeschichte der Wirhellosen Thiere," Ber- 

 lin, 1832. Not having seen it, I can make no further allusion to it in reference 

 to this subject. % Ann. des Sci. Nat. 1832. 



§ Mem. de la Soc. d'Hist. Nat. de Strasbourgh, torn. i. part 2. 



II Bremser published at Vienna, in 1819, a work on the human Entozoa, 

 which in 1824 was translated into French by Grundler and Blainville, and en- 

 riched with many valuable observations from this last author. 



^ \\xt\iox oi Anatomie des Vers Intestinaux. Par. 1824, 4to. ^ 



** Creplin has published two ti-eatises on the Intestinal Worms, one in 1825 

 under the name of Ohservationes de Entozois ; another, entitled Nova Observa- 

 tiones, ^-c. at Berlin in 1829. These works, which I have not seen, are said to 

 contain descriptions of a great many new species, along with many detached 

 observations on these animals. 



■ff Leuckart is the author of a natural classification of Intestinal Worms, in 

 German, published at Heidelberg in 1827. This work has been before alluded 

 to as containing an arrangement in conformity with the principles of Oken. 



