100 ranadjE. 



partly over the back ; and the head is distinguished from 

 the body by a slight contraction at the neck ; and a short 

 period more suffices to bring it to the condition represented 

 in figures 3, 4, of the woodcut, in which the branchiae are 

 seen to consist of two tubercles on each side, as yet simple 

 and undivided ; the holders, which are small simple organs 

 placed near the situation of the future mouth, and which 

 serve to enable the little animal to attach itself by means 

 of a viscid secretion at their extremities, have become 

 longer, the web, or fin, is also enlarged. By this time the 

 first voluntary motion of the embryo is discovered on the 

 application of any means of excitement or disturbance ; but 

 it consists only of a slight movement of the head or tail. 

 The nostrils are seen more distinctly, but the mouth is 

 scarcely yet observable, and shortly afterwards the eye, in 

 a rudimentary state, may be just discerned. The next step 

 in the developement is a slight division of the branchiae into 

 lobes, and the appearance of that beautiful and interesting 

 phenomenon, the circulation of the blood through these 

 organs. The embryo, which is still confined to a curved 

 position by the envelopes (fig. 1), is now seen frequently to 

 extend itself by sudden jerks, as if to emancipate itself 

 from its confinement, which it eventually does by tearing 

 the membrane of the egg. The Tadpoles, we see, are now 

 hatched (fig. 5). According to Eusconi, this takes place 

 within four days after the deposit of the eggs, in a tempe- 

 rature varying only from 2.3° to 27° Centigr. (73°'4 to 

 80 o, 6 Fahr.) ; but certainly in our own climate, in the 

 ordinary temperature of our spring, it does not take place 

 until at least a month. As I before observed, the develope- 

 ment may be greatly hastened by a constant elevation of 

 temperature, and I was often surprised at the degree to 

 which this was the case in the course of my own obser- 



