10 Studies in the Hybrid Bistoninae. IV 



up the next available pair. Again choosing the older male, and se- 

 lecting a female of more recent production, or rather evolution, I mated 

 a pomonaria male with a lapponana female. As a result of the first 

 trial I obtained the folloM^ing sex proportions, 38 males and 39 females 

 and one intersex, and, what is more striking, in a further experiment 

 made to supplement this one, once more another intersex made its 

 appearance accompanied with equality in the numbers of genuine males 

 and females bred. 



Apparently these broods place us in possession of confirmatory facts 

 of great value in pursuing our investigation. The sex potentials 

 in the two species have not been so far apart as to destroy to any 

 great extent the normal equality of the two sexes in numbers. Yet 

 interference has occurred, and that it is not accidental we discern from 

 the appearance of a single half or intersex in each of two distinct 

 broods. 



Now these intersexes give us information of value, not by their 

 advent alone, -but by their actual sexual condition, as is made clear by 

 the following chain of reasoning. Since, in producing males according 

 to the theory propounded above, we are always fusing gametes of like 

 high sex potential, zygotes likewise of high potential should result and 

 such can scarcely be anything else but males. On the contrary, in the 

 fusion of gametes derived from different species and of unlike potential 

 (the outcome of which in ordinary pure forms is the production of 

 females of approximately zero sex level), the result is not of necessity 

 low ; it may actually, as we see by employing figures such as + 50 and 

 — 20, be comparatively high. 



Zygotes of this value, ordinarily fetnales, may make an approach to 

 maleness and some, attaining the mean between the two alternatives, 

 may be thrown to some degree towards it. If approach of the type 

 indicated here was caused in the present broods, according to the 

 scheme laid down, then the insect displaying it should, if we attach 

 due weight to the almost normal sex proportions, be predominatingly 

 female; that such is really the case may be seen by a glance at 

 Text-fig. 10. 



Proof of this kind only makes it the more certain that, conceding 

 the validity of our arguments, if we can make a combination affecting 

 the sex to this extent, further possible combinations should result 

 in the tilting of, not one or two, but of the whole of the females into 

 the condition of intersexes. For testing this, many more species re- 

 main and were utilised. A male rachelae (older) was paired with the 



