HYBRIDS. 113 



Experiments, conducted with the greatest care, were 

 instituted by Pflilger in 1882. He was able to show 

 that different degrees exist in the action of the sperma- 

 tozoa upon the ova of different species. Thus the 

 spermatozoon of a newt (Molge alpcsfrii^, M. vulgaris) 

 acted upon the ovum of Bana temporaria to the extent 

 of producing a very irregular segmentation ; other 

 cross-fertilisations between various frogs and toads 

 extended to the formation of an embryo, of a tadpole, 

 or finally of a perfect Batrachian. These interesting 

 experiments were continued by Pfliiger and W. J. 

 Smith in 1883, and by Born in 1883 and 1884. 



At first Pfliiger absolutely failed in crossing Band 

 temporari(( and B. arvalis, but ultimately both he and 

 Born succeeded in obtaining a few perfect hybrids {B. 

 femporarid c? X B. arvalis ? ). Born also obtained 

 perfect hybrids of Dufo vulgaris and B. viridi.'^ crossed 

 in both directions; and, what is more extraordinary, 

 a few embryos, which did not develop beyond the 

 hatching period, from eggs of Bana escidcnta fecun- 

 dated by Bafo viridis. 



More extraordinary still is a case mentioned by 

 Heron-Royer. In March, 1881, he found amale i?.a7/rf 

 temporaria pairing with a Belohates fuscus which had 

 begun to spawn. Having brought home the short 

 band of eggs, he was much surprised to see them 

 develop quite normally, and ultimately produce larvae 

 which were indistinguishable from those of Bana tem- 

 poraria, ; and two that survived transformed into 

 normal specimens of B. temporaria. I cannot help 

 thinking that some confusion must have taken place : 

 may not, somehow or other, embryos of B. temporaria 

 have been substituted whilst Heron-Royer was observ- 

 ing their development? 



Hybrids between two closely allied species, Bom- 

 hiua'tor igneus and B. pachfij'piis, were obtained by 

 Heron-Royer, and a second generation was produced 

 by crossing these hybrids with individuals of the 

 latter species. It also appears from remarks made 



H 



