26f) INTRODUCTION TO ZOOLOGY. 



The number of species belonging to eacb of these orders is 

 very different, and may be thus stated: 



Tortoises (Testudinata) 69 



Lizards fucrta) 203 



Serpents (Ophidia) 265 



Frogs {Amphibia) 120 



657 



It is interesting to remark the manner in which, according 

 to Berghaiis, the number of species diminishes as we pass from 

 the sunny regions of the East to the duller and more cloudy 

 climes of Western Europe. Thus Italy with her islands can 

 number forty-seven species; France has thirty-one; Great 

 Britain, fourteen ;t and Ireland, it may be added, not more 

 than five. 



It has been stated that the blood of reptiles is cold ; or, in 

 other words, their power of producing animal heat is so feeble 

 that we do not notice any difference between the temperature 

 of their bodies and that of the air or water by which they are 

 surrounded. The same was observed in the preceding group 

 of cold-blooded vertebrata the fishes but arose from a 

 different cause. In the fishes the blood is imperfectly 

 aerated, owing to the small quantity of oxygen with which it 

 comes in contact in the gills. In the highest of the reptile 

 tribes, which breathe exclusively by lungs, these organs are 

 supplied with only a portion of the blood that has circulated 

 through the veins; the other portion is returned into the cir- 

 culation without being purified by exposure to the air. The 

 arteries consequently contain a mixture of blood rendered 

 impure by its previous circulation, and blood recently aerated 



* Berghaiis and Johnston's Physical Atlas, from which admirable work 

 all the information here given, as to the distribution and number of species, 

 is derived. 



f Namely, two Turtles, two Lizards, one Blind-worm, two Snakes, two 

 Frogs, two Toads, and three Newts, 



In a Memoir read before the Royal Society, by Mr. Higginbottom, 

 entitled, " Researches to determine the number of species and the mode of 

 development of the British Triton, the author states, that only two species 

 of Tritons or Newts are met with in England, and that the animals require 

 four years to attain their full growth. "The Triton," he remarks, "pos- 

 sesses the power of reproducing its lost limbs, provided the temperature be 

 within the limits of 58 and 75 Fahrenheit; but at lower temperatures, 

 and during the winter, it has no such power." Athenaeum, April 3, 1847; 

 Annals of Natural History, July, 1847. 



