44 Zoological Collections. Vertebrata. 



This confonnation connects the sloth with the birds, with which it is also related 

 by the ossification of its costal cartilages, representing the sternal ribs of birds, 

 and perhaps by the great number of its caudal vertebras. M. Vrolik, who has 

 confirmed the observation of Vander Hoeven in another individual, thinks that he 

 has remarked the tympanum of the Bradypus didactylus to be hollow externally. 

 This species is more nearly allied to the other mammalia by the normal num- 

 ber of its cervical vertebrae. — {Bijdragen tot de Natuurkundige Wetenschap- 

 pen, Deel. v. st. 1. p. 93.) Ann des Set. Nat. July 1830. 



On the Colouring Matter of the Placenta in the Carnivora Surrounding 



the placenta of the dog, and several others of the Carnivora, there are two circu- 

 lar bands containing a green matter, the nature and use of which has hitherto 

 been doubtful. M. Breschet some time since presented a memoir on this subject 

 to the Philomathic Society of Paris, and in a supplementary paper, recently pub- 

 lished, he has treated at length of the chemical constitution of this substance. 

 He has found, by chemical analysis, that there is an identity of composition be- 

 tween this colouring matter and the green colouring matter of the bile, which he 

 advances as an additional proof in favour of the analogy of functions between the 

 placenta and the liver during the intra-uterine life. These two organs, says M. 

 Breschet, appear to form a little circulatory apparatus in the foetus ; and the co- 

 louring matter of the placenta, or that of the bile, observed in the blood by many 

 chemists, leads us to suppose that this fluid is necessary to the circulation of 

 the blood, and to the maintenance of the life of the foetus, by endowing the 

 blood with the requisite properties. — See the Paper at length, Ann. des Set. Nat. 

 xix. 379. 



Genito-urinary System of the Axolotl of Mexico. — In 1824, Sir Everard 

 Home published an anatomical description of the Axolotl, but with his usual in- 

 accuracy and want of precision ; his account of the genito-urinary organs is par- 

 ticularly superficial. M. Rathke having recently had an opportunity of dis- 

 secting a male and a female of this species of Batrachia, has put us in possession 

 of more correct details on the genital apparatus and the urinary secretion. 



The kidneys of the axolotl resemble those of the tritons and salamanders in 

 form and situation, but they are proportionally smaller. The yellow bodies 

 which accompany the kidneys of the terrestrial salamander, and which are, ac- 

 cording to M. Rathke, the rudiments of supra-renal capsules, are altogether 

 wanting in the Axolotl. The uriniferous ducts cannot be seen without the 

 aid of a lens ; they are very tortuous, and of equal capacity throughout ; they 

 rise from the external edge of the kidney, and pass in a parallel direction to- 

 wards its internal margin. M. Rathke was not able to discover the ureter, 

 probably on account of its delicate structure, and of the veins and cellular 

 tissue which surround it. 



The urinary bladder is small, almost pyriform, and similar to that of the 

 European proteus. 



The testicles have the same position and the same relations as in the sala- 

 manders ; but they diflPer from those of the Triton niger in not being subdivided 

 into many portions. They differ also from those of the Triton tceniatus and 

 T. igneus, in their form not being oval, but flat and elongated. Moreover, they 

 are larger, ccet. par., than the testicles of the neighbouring reptiles, having most 

 analogy with those of the European proteus. 



The vasa deferentia have a great resemblance to those of the terrestrial sala- 

 mander ; they have a similar blackish colour. 



The anal gland is much more developed than in the salamanders ; it only ex- 

 ists in the male. 



In the female the ovaries are proportionally larger than in the terrestrial sala- 

 mander ; the vitellus is not entirely yellow as in this latter species, but half yel- 

 low and half black, as in the frog. 



