Circulation of the Blood. 149 



is that of the capillaries of the system, as in the fish 

 and frog. More than this can, however, be seen, as 

 appears by Mr. Whitney's account of " The Circula- 

 tion in the Tadpole," in the "Transactions of the 

 Microscopic Society," vol. x. 1862. The heart was 

 distinctly observed with its various vessels, and the 

 narrative may be read in Dr. Carpenter's work on the 

 microscope, accompanied by a figure of the tadpole. 

 Dr. Carpenter adds that it shows the structure just at 

 a time when the animal is neither fish nor reptile, and 

 is the more remarkable in a physiological point of 

 view. The great interest attaching to such an obser- 

 vation, when conducted with due knowledge of the 

 true points of inquiry, may excuse the training, or 

 rather starving process which was used to render the 

 tadpole transparent, and which is politely described as 

 an exclusively water-diet. For myself, I should feel 

 satisfied with the spectacle presented by the beautiful 

 little water-newt, which possessed the requisite trans- 

 parency without any special treatment. 



The newt is called by Linnasus Lacerta aquatica, 

 or the water lizard, but is now correctly classed with 

 the amphibia, from its affinity to that group in various 

 respects, including the completeness of its transfor- 

 mation from the condition of a fish to that of a reptile. 

 For although it continues in its full-grown state to be 

 rather more aquatic in its habits than the frog, and 

 retains its long tail instead of losing it by absorption, 

 it exactly resembles the frog and toad in the early 

 possession of branchiae, which are subsequently lost and 

 replaced by lungs, suited for breathing atmospheric air. 



