AMPHIBIA. 



105 



nostrils, the tongue, the eyes, and the ears 

 were gone; the animal could therefore enjoy 

 no relation to external objects but by the sense 

 of touch. It nevertheless evinced conscious- 

 ness, creeping cautiously and slowly about, 

 occasionally raising the neck to the surface as 

 if attempting to breathe. The process of cica- 

 trization at length completely closed the aper- 

 tures of respiration and of deglutition. It lived 

 three months after the operation, and then died 

 from accidental neglect. After all, this expe- 

 riment proves only the respiratory function of 

 the skin, a fact already sufficiently established 

 by the observations of Dr. Edwards before 

 detailed, and its cruelty does not appear to be 

 compensated for by its results. 



XV. Of reproduction. The impregnation 

 of the ova in the amphibia, is effected without 

 actual coitus; that is to say, it either takes 

 place out of the body, as in the anoura, or the 

 impregnating fluid is received by the mere 

 contact of the external opening of the cloaca 

 in the two sexes, as in the tailed forms. The 

 only exception to this statement is in the land 

 salamander, the male of which has a small 

 intromittent organ. The act itself of impreg- 

 nation therefore differs materially in these two 

 divisions of the class. The generative organs 

 of both sexes are double, and are placed sym- 

 metrically in the abdomen. The testes in the 

 higher forms of the class, the frogs and toads, 

 are small globular oval bodies, having exter- 

 nally a bright white appearance, from the 

 tunica albuginea, and internally a somewhat 

 loose texture, and a yellowish colour. They 

 are placed behind the liver, attached to the 

 vertebral column ; the vasa deferentia are 

 numerous, disposed in pairs; they form a 

 small epididymis, and passing on the outer 

 side of the kidneys back towards the cloaca, 

 dilate into vesiculae seminales, just before they 

 terminate in that cavity. These organs, as in 

 many other animals, become much enlarged at 

 the breeding season. 



The ovaria are situated in the anterior and 

 upper part of the abdomen, and are internally 

 divided into numerous sacs, by duplicatures 

 of the peritoneum, by which also they are 

 bound to each side of the spine. These sacs 

 are torn at the period of depositing the eggs, 

 whether by the pressure of the arms of the 

 male, as asserted by Prevost and Dumas, or 

 otherwise, appears uncertain. The oviducts are 

 small at their commencement, and become 

 large towards their termination in a sort of 

 dilated sac, which Altena terms the uterus; 

 they are of a pulpy substance, having an in- 

 ternal secreting surface; and the eggs during 

 their passage through them become enveloped 

 in a gelatinous mass. They dilate into a sort 

 of uterine cavity just mentioned, which opens 

 into the cloaca. 



The mode by which the eggs of the frog 

 pass from the ovaries into the oviducts appears 

 yet to be doubtful. The observations of Pre- 

 vost and Dumas on this subject are generally 

 received as correct, but their statements are 

 denied in some particulars by Altena, and 



doubted in others. They state that the ova, 

 detaching themselves from the ovaries, are 

 seized by the opening of the tube, but they do 

 not state the mode by which this act is effected. 

 It is a question which was long since examined 

 with great care by Swammerdam, and which 

 brought him into a controversy ; and he con- 

 fesses at last his ignorance of the mode in which 

 it actually takes place. 



The ovaries enlarge greatly at the breeding 

 season, and the ova at the time of their depo- 

 sition fill the body almost to bursting. At the 

 time of impregnation the male placing himself 

 on the back of the female, embraces the body with 

 astonishing force with the anterior legs, which 

 are pressed under the axillae, and the tuber- 

 cular thumbs, which are at this period con- 

 siderably enlarged to enable him to retain his 

 hold, are so essential to this object, that if 

 they be cut off, he can no longer clasp the 

 female with the requisite force. The instinct 

 which instigates the male frog to this act at the 

 season of breeding is astonishingly powerful, 

 and sometimes no less remarkably blind. 

 Thus, it is recorded by Walter, and has been 

 often observed by others since his time, though 

 the object of this curious fact has been un- 

 accountably overlooked, that frogs are occa- 

 sionally found in the spring adhering with 

 great force to different parts of the skin of 

 pike ; and a near relative of the writer of this 

 article has seen an instance of the same kind, 

 where several frogs were so closely fixed to a 

 large pike as to require some force to remove 

 them. This instinct of adhesion is, in feet, 

 sometimes fatal to its legitimate object. I have 

 before now taken from the water a large con- 

 glomeration of male frogs, amounting to per- 

 haps twelve or more, with one solitary female 

 in the middle of the mass, dead and putrid, 

 and even some of the males, towards the in- 

 terior, pressed into an almost lifeless and shape- 

 less lump. 



While the male is thus closely embracing 

 the female, an operation which sometimes lasts 

 for more than a month, the eggs, to the num- 

 ber of several hundreds, are gradually ejected 

 from the cloaca, either in masses as in the 

 frog, or in double chaplets as in the toad, an 1 

 impregnated by the sprinkling of the semen, 

 as they pass out under the male. In some 

 species, as the bufo obstetricans, the female is 

 assisted in the act of expulsion by the hinder 

 legs of the male. When the eggs are thus 

 deposited in the water, the jelly-like substance 

 in which each is enveloped absorbs a large 

 quantity of it, and the whole mass speedily 

 enlarges to many times the size of the animal 

 from which it was expelled. 



The male of the bufo obstetricans just men- 

 tioned, when, by his assistance, the eggs are 

 excluded, attaches them to his thighs by glu- 

 tinous threads, and carries them about with 

 him until the young are ready to leave them, 

 when he seeks a pool of water in which he 

 deposits them, and the young shortly afterwards 

 come forth. 



The impregnation of the tailed aquatic 



