262 Genetical Studies in Moths 



somes respectively, so that in forming the F.^, generation a combination 

 of any two of these takes place. Thus the F^ zygotes commence life 

 with a mechanism intended to deal with 76 chromosomes at the most, in 

 place of which 86 may occur in each nucleus. Consequently, in their 

 gametogenesis, in addition to failures in homology, merely mechanical 

 complications ensue ending not only in chromosome disturbance but in 

 their actual loss and degeneration in the cytoplasm. In this case, if the 

 chromosomes' be in very truth the heredity bearers, then there cannot 

 but be a manifestation of new characters or combinations in the 

 imagines. The great uniformity of the F^ pseudo-mutants, however, 

 suggests that if this explanation is, as is almost certainly the case, true, 

 then there must be some preferential setting up of some individual type 

 of chromosome combination. Still it is quite possible that the other 

 types may not render the zygotes possessing them in any way worthy of 

 special note. 



To my mind the importance of this result is very great ; the parallel 

 nature of the occurrence with those secured by De Vries and others in 

 Oenothera suggests just as forcibly to me, as did other considerations to 

 Bateson, that Oenothera Lamarckiana was and is not a pure type, and 

 not being pure is no fit subject for ordinary genetical experiment, 

 especially when no one has the faintest knowledge of its actual genotypic 

 composition. Much less then can it be held a fit subject upon which to 

 base such a fundamental doctrine as mutation. In thus pointing out the 

 views I have been led to adopt concerning Oenothera I do not wish to 

 deny that mutation occurs : that it does we have ample evidence in our 

 own genus in the latifasciata aberrations of both autumnata, filigram- 

 maria and dilutata, not to mention other well-known cases both in 

 domesticated and wild animals and plants. 



The Back Gross between the F^ % and O. autumnata (/". 



This was reared from a pairing of an autumnata male of the feebly 

 marked, suffused pinewood form and a medium female from the F^ lot. 

 Ova were successfully obtained and wintered safely to emerge just prior 

 to autumnata in the succeeding spring. The larvae revelled in the haw- 

 thorn they were oflfered and fed up rapidly without loss. 



Of the larvae and pupae little can be said save that almost no signs 

 of filigrammaria influence were discernible unless they lay in the 

 slightest possible strengthening of the longitudinal stripes, the darker 

 ground of head and body in filigrammaria failing to show any effect. 



In the imagines (save in size) one looks likewise in vain for any 



