DEVELOPMENT. 



209 



ing its mode of life. In the development of the common 

 Crab, so different is the outward form of the newly 



FIG. 173. Metamorphosis of the Mosquito (Culex-jripiens) : A, boat of eggs ; 8, some 

 of the eggs highly magnified ; d, with lid open for the escape of the larva, C ; D, 

 pupa; E, larva magnified, showing respiratory tube, e, anal fine,/, antennae, g; 

 F, imago; a, antennae; 6, beak. 



hatched embryo from that of the adult, that the former 

 has been described as a distinct species. 



The most remarkable example of metamorphosis among 

 Vertebrates is furnished by the Amphibians. A Tadpole 

 the larva of the Frog has a tail, but no legs ; gills, in- 

 stead of lungs; a heart precisely like that of the Fish; a 

 horny beak for eating vegetable food, and a spiral intes- 

 tine to digest it. As it matures, the hinder legs show 

 themselves, then the front pair; the beak falls off; the 

 tail and gills waste away; lungs are formed; the diges- 

 tive apparatus is changed to suit an animal diet ; the heart 

 is altered to the Reptilian type by the addition of another 

 auricle ; in fact, skin, muscles, nerves, bones, and blood- 

 vessels vanish, being absorbed atom by atom, and a new 

 set is substituted. Moulting, or the periodical renewal of 

 epidermal parts, as the shell of the Lobster, the skin of 



14 



