426 REVIEWS. 



rata which should be substituted in their stead, naturalists still hold 

 different opinions. These discrepancies, happily, exist less in appear- 

 ance than in reality, and for the most part, as will presently be made 

 clear, are of a secondary or non-essential character. 



Under the name of Hydromedusse 38 Vogt, 39 Sars, Leuckart, G-egen- 

 baur and J. V. Cams acknowledge a very natural class, including the 

 Hydroid Polypes (Hydra, Corynidse and Sertularida?) together with 

 the Siphonophora and Discophora. Bronn, 40 however, separates the 

 HydromedusaB into two classes ; Hydra? and Medusae, of which the 

 first contains but one genus, Hydra. 



Milne Edwards, also, has recently assigned Hydra to a separate class. 

 The same distinguished zoologist 41 further suggests the restoration of 

 the old term Acalephse to designate a group including, besides the 

 Hydromedusa? of Vogt, the well-marked order Ctenophora, or, in other 

 words, all the Acalepha? of Eschscholtz, together with the Hydrozoa 

 of Owen. Such, too, is the opinion of Agassiz. 42 But while this natu- 

 ralist considers all these " Acalephae" as forming a single class, Milne 

 Edwards does not hesitate to divide them into, at least, three distinct 

 classes, — " Les Medusaires, les Siphonophores et les Hydraires." 



In the accompanying table, the latest views of Milne Edwards, 

 both as to the systematic position and primary divisions of Coelen- 

 terate animals are exhibited in a compendious form. 



Embeanciiement des Zoophytes. 



i 



Saecodaiees. Eadiaiees. 



ECHI]S"0DEEMES. CcELENTEEES. 





Classe 1. Acalepues. 



( , N 



Classe 1. Classe 2. Classe 3. 



Coealliaiees. 

 1. 



HVDEAIEES. SlPKONOPlIOEES. Medusaiees. 



38 Leuckart (Bericht in Wiegmanns's Arch.) terms the class Hydrasvxedusce ; and 

 Gegcnbaur ( Op. s. cit), Ilt/dromerfvsvla. See note 34 p. 423. 



39 In his Zoologische Briefe, 1851, the group HydromedusEe, as established by 

 Vogt, does not include the Siphonophora, of which he makes a separate class. But, 

 in 1853, he fully recognizes their true affinities, regarding them as but an order of 

 his class Hydromedusaj. (Gen. Inst., Tom. I., p. 144). 



40 Op. s. cit. pp. 78 & 85. Bronn arranges the Ccelcnterata under four classes 

 Polypi, Hydra:, Medusre, and Ctenophora. 



41 Op. s. cit. p. 4. Here no special mention is made of the Ctenophora, but there 

 can be little doubt that Prof. Milne Edwards considers them as constituting a sub- 

 division of his class Medusaires. A perusal of pp. 301 — 306 of the fifth volume of 

 his Lecons sur la Physiologie, published in 1859, appears further to confirm such a 

 conclusion. 



42 Essay on Classification, 1S59, p. 294. 



