226 PROBLEMS OF GENETICS 



that we have as yet only a small selected part of the evidence 

 before us, even as concerning the effect of temperature on the 

 cross between signaticollis 9 X diver sa cf . We learn that at 

 the lower temperatures the result was eleven times the expected 

 one, and six times an unexpected one ; further, that we owe it to 

 the author's inadvertence that we have come to hear of the 

 expected result at all, and that though he knows the factors 

 which determine the discrepancy, he declines for the present to 

 name them. In these circumstances we can scarcely venture as 

 yet to estimate the significance of these records. 



The paper goes on to recount somewhat comparable, but more 

 complex instances in which the descent of the colour of adults and 

 of larvae was affected by temperature in crosses between un- 

 decimlineata and signaticollis. As they stand the results are 

 very striking and unexpected, but I think, in view of what has 

 been admitted respecting the former part of the paper, full dis- 

 cussion may be postponed till confirmation is forthcoming. 



One feature, however, calls for remark. This second paper is 

 written apparently without any reference to the discoveries 

 related by Tower in his previous book, to which no allusion is 

 made. This is most noticeable in the case of an experiment in 

 which ( p. 296, H. yooA ) undecimlineata 9 (the dominant) 

 was mated to signaticollis o 71 with the result that all the offspring 

 were undecimlineata and bred true to that type (Parthenogenesis 

 was tested for, but never found to occur). This experiment was 

 made at a temperature averaging 95 F. =1= 3.5 by day and 89 F. 

 =t= 4.8 by night, and in a humidity given as 84 per cent, by day 

 and 100 per cent, by night; but in the previous book (p. 294) we 

 are told that pure undecimlineata bred together "under an ex- 

 treme stimulus of high temperature, 10 C. above the average" 

 and a relative humidity of 40 per cent, gave n beetles only, 

 all angustovittata. But reference to the Plate 16, Fig. 2, shows 

 that angustovittata must be exceedingly like signaticollis, having, 

 like it, the elytral stripes obsolete, and if there is any marked 

 difference at all, it can only be in the larvae. It seems strange 

 that if undecimlineata really gives off ova of this recessive type at 

 high temperatures, the fact should not be alluded to in connection 



