xxiv HISTORICAL INTRODUCTION 



eggs reach the oviduct together. Only one, however, in each oviduct 

 develops, the remaining eggs fusing to form a common yolk-mass 

 which serves for the nourishment of the surviving embryo, who is 

 thus the 'assassin of his brothers and sisters' (Dumeril). The gills 

 are half the length of the entire body and extend backwards to the 

 hind limb, but they degenerate before birth, and the young are pro- 

 duced in the adult state with scarcely any trace of the gills, and none 

 of the gill openings. This is ascribed to the fact that atra lives in 

 situations where water may be scarce or not available, and hence the 

 metamorphosis must be completed within the uterus. Schreibers 

 asserts that he has observed atra in captivity coupling in water as in 

 the Frog, and that if the larvae of maculosa are forcibly kept under 

 water the metamorphosis may be delayed for many months. 



The spermatozoa of the Salamander were first described by Pre- 

 vost and Dumas in 1821. The work of Dutrochet (182 1-2), al- 

 though it relates to Triton only, may be mentioned as containing the 

 first account of the 'internal' gills of the Amphibian larva. He also 

 makes the suggestion that the regeneration of the limbs and tail is 

 not a case of preformation, but of the epigenetic development of parts 

 much as they were originally produced in the embryo. The ear of 

 Salamandra and its semicircular canals were re-described by Blain- 

 ville in 1822. He says that there is no trace of a tympanic cavity or 

 Eustachian tube, but adds (incorrectly) that these parts are well 

 developed in the larva. He shows for the first time that the oper- 

 culum which closes the fenestra vestibuli, thereby taking the place 

 of the auditory ossicles, can be moved by a component of a shoulder 

 muscle (M. opercularis). Two years later Huschke, also working at the 

 auditory organs of Salamandra, confirms the absence of a tympanic 

 cavity and Eustachian tube, and asserts that the operculum is rather 

 a detached portion of the skull (as it is) than a true ear bone. He 

 found that the operculum was elastic, and would spring back into its 

 place after it had been pulled up. He holds that the columella and 

 ear ossicles arise from the anterior gill arches, that the tympanic 

 cavity represents the gill cavity of the fish, and that the Eustachian 

 tube is an inner gill opening. 



Dr. J. Davy, the younger brother of Sir Humphry Davy, was the 

 first author after Hunter to throw any light on the structure of the 

 Amphibian heart. He did not examine the Salamander, but his work 

 has general bearings which are too important to be disregarded. In 

 his first communication of 1826 he finds that the heart of toads and 

 frogs consists of two auricles and one ventricle, the auricles being 

 separated by a fibrous septum, and he considers it probable that the 



