1030 



A. W. BLACKLER AND M. FISCHBERG 



The toads were measured and weighed at 3 y 2 and 5 y 2 years of âge and little 

 différence was found between the figures for the two déterminations. Females 

 averaged 77 mm. in length and weighed an average of 54 gms., while the maies 

 averaged 66 mm. in length and 31 gms. In thèse respects therefore, and in the 

 absence of much variation in length and weight, the hybrid toads were interme- 

 diate between Xll and Xlp. 



Fig. 8. 



Dorsal surface of maie hybrid X. 1. laevisQ/petersi 6*. 

 Length 74 mm. Note petersi-like markings (compare Figs. 4 and 1). 



b) XlpQ x XU$\ This cross has been performed five times, of which the firstt 

 attempt failed to yield cleaving eggs and the second yielded very few. The remain- 

 der ail gave cleavage in the order of 70%. In thèse matings, however, up to 40% 

 of the tadpoles developed tails with a dorsal or ventral bend, failed to commence 

 feeding, and died. It may be, in conséquence, considered that there is some r 

 incompatability between the two species in this hybrid combination, presumably ) 

 mediated via some maternai influence (since the hybrid génome is presumablyl i 

 the same as in the reverse hybrid). However, there are two factors which militate 

 against such a conclusion in the absence of more knowledge ; the tadpoles which i 

 did not show the tail abnormality continued their development without crisis and 

 eventually gave perfectly normal toads, and abnormality of the tail is often asso- 1 

 ciated with the development of an egg of poor quality. 



The Xlp eggs cleaved in the petersi manner, the third cleavage sharply dividing I 

 the animal pigment offfrom the rest of the egg. The appearence of the true mêla- ' 



