234 Mr. F. E. Bedckrd on the 



tlieir origins from the dorsal aorta and their points of entrance 

 into the thickness of the dorsal parietes. 



They arise at unequal intervals from the aorta and enter 

 the parietes at varying distances from each other. In Pi/fkon 

 reticulatus, Hopkinson and Pancoat * did not figure these 

 arteries at all ; but Jacquart t in another python figured 

 them as single arteries arising regularly from the aorta J. 

 1 do not find this in Python spi/otefi. But as the conditions 

 in Eryx are more primitive still, I refer to that snake only 

 for the present. Here the intercostal arteries are practically 

 regular in their arrangement, being metamerically disposed 

 in agreement with the vertebrae. Tiiere is a pair to each 

 intervertebral interval. The two arteries of the pair either 

 arise side by side from the aorta, or an artery single in its 

 origin soon bifurcates. I cannot but tliink that this arrange- 

 ment of the intercostals is more primitive than that which 

 is more usual among the Ophidia. I may remark that it 

 cccurs in the Lacertilia (e. g. Chumreleon, PUiqna, &c.). 



I am uncertain whether to regard the total absence of a 

 gubernaculum, tying down the ventricle to tiie pericardium, 

 as indicative of a primitive structural relationship. It may 

 at first appear unnecessary to record the fact of the absence 

 of a gubernaculum. For it is generally stated § that the 

 Ophidia are to be contrasted with the Lacertilia in this very 

 point — the Lacertilia possessing a gubernaculum and the 

 Ophidia being deprived of one. I find, however, considerable 

 vestiges of this " tag " in certain Ophidia, but not in Eryx 

 or Boa. On the other hand, I think it may be regarded as 

 probable that a conspicuous azygos vein is a primitive 

 feature. Now in Python spilotes this vein collects blood 

 from and therefore extends over many more than four inter- 

 costal spaces, which is the limit of this vessel in Coronella 

 getula. In Eryx conicus the azygos vein collects blood from 

 no less than ten intercostal spaces. 



As a general rule a considerable number of renal arteries 

 (even as many as eight in Coluber catenifer) supply each 

 kidney. This is correlated with the considerable length of 

 the gland in most snakes ; I cannot, however, ascertain that 

 there is an exact relationship between the length of the 

 kidney and the number of arteries supplying it. But the 



* Trans. Amer. Phil. Soc. v. 1837, p. 121. 



t Ann. Sci. Nat. (4) iv. p. 321. 



\ In Python Selics 1 find an identical arrangement. The arteries arise 

 singly and bifurcate just before entering the parietes. 



§ For instance, in that section of Bronn's ' Klassen uud Ordnungen des 

 Thierreichs' which deals with snakes. 



