698 



A HISTORY OF 



shall find that it has a very little brain for 

 its size ; a very wide swallow ; a stomach 

 seemingly small, but capable of great disten- 

 tion. The heart in the frog, as in all other 

 animals that are truly amphibious, has but 

 one ventricle; so that the blood can circulate 

 without the assistance of the lungs, while it 

 keeps under water. The lungs resemble a 

 number of small bladders joined together, 

 like the cells of a honey-comb: they are 

 connected to the back by muscles, and can 

 be distended or exhausted at the animal's 

 pleasure. The male has two testiculi lying 

 near the kidneys ; and the female has two 

 ovaries, lying near the same place : but 

 neither male nor female have any of the ex- 

 ternal instruments of generation; the anus 

 serving for that purpose in both. Such .are 

 the most striking peculiarities in the anatomy 

 of a frog; and in these it agrees with the 

 toad, the lizard, and the serpent. They are 

 all formed internally pretty much in the same 

 manner, with spongy lungs, a simple heart, 

 and are destitute of the external instruments 

 that serve to continue the kind. 



Of all those who have given histories of 

 the frog, Mr. Raesal, of Nuremberg, seems 

 the most accurate and entertaining. His 

 plates of this animal are well known ; his 

 assiduity and skilfulness in observing its 

 manners are still more deserving our esteem. 

 Instead, therefore, of following any other, I 

 will take him for my guide; and though it 

 be out of my power to amuse the reader with 

 his beautiful designs, yet there will be some 

 merit in transcribing his history. 



The Common Brown Frog begins to couple 

 early in (he season, and as soon as the ice is 

 thawed from the stagnating waters. In some 

 places the cold protracts their genial appe- 

 tite till April; but it generally begins about 

 the middle of March. The male is usually 

 of a grayish brown colour; the female is 

 more inclining to yellow, speckled with 

 brown. When they couple, the colours of 

 both are nrarly alike on the back; but as they 

 change their skins almost every eighth day, 

 the old one falling off in the form of mucus, 

 the male grows yellower, and the female 

 more brown. In the males the arms and legs 

 are much stronger than in the females; and 

 at the time of coupling, they have upon their 



thumbs a kind of fleshy excrescence, which 

 they fix firmly to the breast of the female. 

 This Linnaeus supposed to be the male in- 

 strument of generation; but, by closer in- 

 spection, it is tound only of service in hold- 

 ing the female in a more strict embrace. It 

 may be cut oft" and the impregnation con- 

 tinue unimpaired : it is sometimes found in 

 the opposite sex; and some of the males are 

 found entirely without it: however, when it 

 is cut off, the male cannot hold the female so 

 strongly as before. 



The sex couple only once a year; and 

 then continue united sometimes for four days 

 together. At this time they both have their 

 bellies greatly swollen; that of the female 

 being filled with eggs ; the male having the 

 skin of the whole body distended with a lim- 

 pid water, which is ejected in impregnation. 

 As soon as the male has leaped upon the fe- 

 male, he throws his fore legs round her 

 breast, and closes them so firmly, that it is 

 impossible with the naked hands to loose 

 them. The male clasps his fingers between 

 each other, in the same manner as people 

 when they are praying; the thumbs press 

 with their thickest sides against the breast 

 of the female ; and though she should strug- 

 gle ever so much, nothing can induce him to 

 let go his hold. The grasp seems involuntary 

 and convulsive ; they cannot be easily torn 

 asunder; and they swim, creep, and live 

 united, for some days successively, till the 

 female has shed her spawn, which at length 

 she does almost in an instant. But how the 

 impregnation is performed, without any ap- 

 parent instruments of generation, has long 

 been an object of inquiry ; and still continues 

 in great obscurity. To investigate the diffi- 

 culty as carefully as possible, .our German 

 philosopher continued to examine their mu- 

 tual congress for three years together, and 

 availed himself of all the lights that the knife, 

 or analogy, could furnish. 



After having chosen twelve couple of frogs 

 that were thus joined to each other, and 

 having placed each couple in a glass vessel 

 with water, he scarcely let them out of his 

 sight day or night, and even sat up two nights 

 together to examine their operations. The 

 first day he observed nothing that deserved 

 remark ; but the second they began to be 



