272 CLASSIFICATIONS OF THE AMPHIBTA 



cliia, denotes that the gills (so far at least as is yet known) 

 are always wanting : and another, Imperfectibranchia, sig- 

 nifies that the gills are either by nature imperfect, or that we 

 have only at present an imperfect knowledge of them. The 

 latter, as will be supposed, I have introduced as a provisional 

 order. This arrangement will be found also to combine all 

 the characters given in the last three classifications. I have 

 likewise considered it preferable to agree with that systematic 

 writer, and several others of the present day, in making the 

 Amphibia constitute an entire Class by themselves. Yet I 

 ought to state, that one of the distinctions relied upon for 

 that object by some zoologists, — respecting the heart of these 

 animals having but one auricle, and one ventricle, (cor unilo- 

 cular uniauritum), — and in which Cuvier himself especially 

 coincided; for, even in his last edition (1829) of the c Regne 

 Animal,' he remarks that the single auricle is common to, 1 

 and therefore characteristic of, the Batrachian order, — does 

 not in reality exist, as Prof. Owen lately discovered in his 

 very skilful dissections of the hearts of some of the doubtful 

 species, and in particular of that of the Siren lacertina. 7 - It 

 appears then from the accounts mentioned in his paper, which 

 is published in the ' Zoological Transactions,' (vol. i. p. 213, 

 1835), that the heart of the Amphibia has one uniform exte- 

 rior, but is in the interior separated into two distinct auri- 

 cles. 2. That distinguished comparative anatomist observes 



1 His words are, — " n' ont au cceur qu' une seule oreillette, et un seul ven- 

 tricule." — 'Regne Animal,' tome ii. p. 101. 



2 See the beautiful preparations of the Siren, numbered 912, 913, 914 ; 

 and particularly 913, A, which shows the internal structure of the two auri- 

 cles in the heart of that animal, — in the Museum of the Royal College of 

 Surgeons, in London. 



3 Hunter instituted an elegant system of classing those animals which 

 have a heart {tcaftia) by its cavities, (xoihicci) ; — " for in some animals" (as 

 he observes) " it has only one, others two, others three, and the most com- 

 plete of all four cavities ; and this difference of structure forms so many 

 grand divisions of the animal kingdom, which I must be permitted to call 

 by the names of Monocoilia, Dicoilia, Tricoilia, and Tetracoilia." — (See 

 Phys. Cat. vol. ii. p. 147). In the third order, Tricoilia, he places all the 

 Amphibia, Linn., from their having two auricles and one ventricular cavity; 

 but his pneumobranchiate tribe he referred to the second order, Dicoilia, 

 from their having only one externally visible auricle, and one ventricle. — 

 The Radiata were named Acardia. Upon this system Mr. Owen justly re- 

 marks, — " like all classifications founded on the variations of a single organ, 

 the cardiac arrangement is too artificial for general application. — "(Note in 

 loc. cit.) The same objection cannot equally apply to the branchial classi- 

 fication here proposed, because the absence and presence of gills form distinct 

 and externally apparent characteristics in these animals ; whereas, on the 

 contrary, the chambers of the heart, being internal organs, can only be ex- 

 amined by very careful dissections. 



