REPORT ON ZOOLOGY. 233 



marine animals discovered by them the year before in the Straits 

 of Gibraltar, where they were detained some days by a calm 

 soon affeer the commencement of a second voyage with Captain 

 D'Urville. Amongst these are several new genera belonging to 

 the group of Diphyes, Cuv., which the authors consider as en- 

 titled to rank as a family. This memoir contains by far the 

 most valuable details respecting the organization of these re- 

 markable animals which had appeared up to that time. In 1828, 

 Rang published in the M4m. de la Soc. d'Hist. Nat. de Paris* 

 a memoir on the genus Beroe, which he considers as forming 

 another distinct family amongst the free Acalepha, in which he 

 describes two new genera. Rang thinks that the free Aca- 

 lepha may be divided into three families, having for their re- 

 spective types Beroe, Medusa, and Diphya. The characters of 

 these he proposes to take from the organs of locomotion. In 

 the first {Beroides, Rang,) they consist of a number (always an 

 even number) of longitudinal ribs formed by very numerous se- 

 ries of small ciliae ; in the second (Medusaires), these organs 

 are membranes, sometimes entire, sometimes fringed or cut into 

 leaflets, and ranged in a circle round an umbrella ; in the third 

 {Dip hides), these organs are found only in the margin of the 

 principal opening, and sometimes also in a membrane bordering 

 the circumference of it. 



By far the most valuable work which has yet appeared in this 

 department of zoology is said to be the System der Acalephen, 

 8^-c. of Dr. Eschsholtz, published at Berlin in 1829t. Its author 

 is well known as the naturalist who accompanied Captain Kotze- 

 bue in his voyage of discovery, and as having some time back 

 published valuable observations on the Physalice, Porpitce, aiid 

 Velella;, made by himself during that voyage^. In the present 

 work he has given a detailed account of the structure of the 

 Acalepha in general, as well as presented a new arrangement of 

 these animals. Their organization, according to his researches, 

 would seem to be of a more complex nature than was formerly 

 supposed. He has discovered a very perfect vascular system in 

 the Beroe tribe, which has led him to place this group at the 

 head of the series. In his classification he adopts three orders, 

 Ctenophora, Discophora, and Siphonophora, the characters of 

 which are taken from the presence or absence of a central diges- 

 tive cavity, and from the form and structure of the organs of lo- 

 comotion. 



* torn. iv. p. 166. 



t I have not seen this work myself. The above notice of it is from the Bull, 

 des Set. Nat. (1831), tom. xxiv. 



t See Kotzebue's Voyage, vol. iii. Append. 



