96 RANID.E. 



maximum of developement, constitutes one of the most 

 charming objects for microscopic observation which can be 

 conceived, and to view which a very high power is not ne- 

 cessary, nor even desirable. The current of the blood poured 

 in regular pulsations at each contraction of the heart, passes 

 up each stem or main branch of the branchiae, and a distinct 

 stream is given off to each leaf ; it is propelled to the ex- 

 tremity, and then returns down the opposite sides in the 

 most regular manner, and the parts are so transparent that 

 every globule of blood is distinctly and beautifully visible. 



This state of things, however, is destined to last but a 

 short time. No sooner have these interesting organs attain- 

 ed their greatest developement than they begin to diminish 

 in size ; they become obtuse (fig. 7), and are gradually so 

 reduced as to be withdrawn within the branchial cavity, and 

 concealed by a little operculum of the integument. The 

 eyes are now perfectly formed. The holders have become 

 much diminished in size ; the mouth has acquired moveable 

 lips, and has changed its position from the inferior part of 

 the head to near the extremity, and the little creature which 

 has hitherto derived its sustenance either from its own re- 

 sources or by absorption, now seeks its food amid softened and 

 decomposing vegetable matter. The caudal web (fig. 8) has, 

 therefore, become considerably developed, and serves for very 

 rapid as well as varied locomotion. The colour of the body, 

 too, has undergone a considerable change, having become of 

 a soft olive green, the abdomen being dotted with golden 

 yellow. 



The Tadpole now undergoes but little change in its ex- 

 ternal form for a considerable time, but increases rapidly in 

 bulk, and by and by a little tubercle appears on each side of 

 the vent, which is the rudiment of the posterior extremity ; 

 this soon acquires somewhat the form of the perfect limb, the 

 toes budding, as it were, at the extremity, but it still con- 



