of the Surinam Toad. 271 



the male has spread the spawn on the back of the female *, 

 or do they owe their origin to previously existing structures, 

 the cutaneous glands perhaps, which receive the ova and 

 then by enlargement and transformation become the brood- 

 cavities ? 



Passing over the authors who wrote upon the remarkable 

 genus Pipa in the second half of last century, since the 

 question that is here raised did not appeal to them, we have 

 first to consider the statements of Mayer, the former Professor 

 of Anatomy in the University of Bonn f, who writes as 

 follows : — " Before the time of oviposition no cells are discern- 

 ible upon the back, but merely wart-like folds of skin, the 

 interspaces between wliich probably form the actual cells 

 later on. These cells develop, and are closed by means of a 

 cornea-like operculum." Since there is no mention here of 

 glands, we may well follow other writers in regarding 

 Mayer's words as implying that he considered the alveoli to 

 arise as the result of a kind of invagination of the skin. 



Ten years later the same observer examined Xenopus Boiei, 

 Wagl., which, as a tongueless Batrachian, is allied to Pipa 

 dorsigera, and was even named by Mayer PiiJa africana^ as 

 opposed to P. americana {dorsigera) %. 



Supposing that Xenopus^ " similarly to Pipa surinamenais 

 (a»2e/-2cana) , receives her eggs on her back and hatches them," 

 the author proceeds to the structure of the integument : this 

 is stated to be more vascular in the female than in the male 

 or in the common frog, and to be also thicker and firmer. On 

 its inner surface may be seen " innumerable fine pits," which 

 also become visible on the exterior j but we are told that 

 especially conclusive in favour of the author's view is the 

 fact that in the case of one of the female specimens the skin 

 on the back is peeled off, and that, moreover, one may ob- 

 serve with the naked eye rounded pits, " large enough to 



* [Prof. Leydig here alludes to the customary idea of the process as 

 represented in the natural histories. At a meeting of the Zoological 

 Society of London, held on May 5th of the present year, an interesting 

 communication was read from Mr. A. D. Bartlett on the breeding of these 

 toads in the Society's Gardens. The precise manner in which the eggs 

 find their way on to the back of the female has long been a puzzle to 

 naturalists ; and when ]\Ir. Bartlett's observations are published it will be 

 found that the part played by the male in the spreading of the ova on 

 the mother's body is rather a mechanical than an active one, as hitherto 

 suppo sed . — Tr ANSL . ] 



t A. F. J. C. Mayer, " Beitriige zu einer anatomischen Monographic 

 der Gattung Pipa" Nov. Act. Leop.-Carol. nat. cuiios. 1825. 



t A. F. J. 0. Mayer, ' Arbeiten fiir vergleichende Anatomie ' (Bonn, 

 1835). 



