Different Genetic Possibilities within the Balance Theory 435 



later this situation {mutatis mutandis) in Melandriwn. If this were 

 so, 3A 2X should be an intersex (male intersex), though it is possible 

 that the F factors in tlie autosomes are so weak that 3A would still 

 not affect the 2X action. If 4 or 5 A with 1 or 2X could be obtained, 

 the problem could be answered. Regarding the M factors in the 

 X-chromosomes, we may postulate them, but the data of the table do 

 not prove their existence. It would be proved if 2A 3X or 4X and Y 

 turned out to be female intersexes. So far, we know nothing more but 

 that the Y in Boynbyx has an overwhelming female influence, while 

 the rest of the genetic system is still unknown. 



It would be of great interest to know the genetic situation in 

 plants with female heterogamety like Fragaria. A cytoplasmic pre- 

 determination in the plant egg is very improbable in view of the type 

 of determination in plant development, which is so different from 

 that in animals. However, thus far (see Staudt, 1952) nothing is 

 known about localization of F and M. 



b. Male heterogamety 



Very different are the expectations in male heterogamety. Here 

 the egg has no Y-chromosome, which is present only in the male line, 

 and therefore a straight balance system between X- and Y-borne sex 

 determiners is impossible. This means either that sex determination 

 works without a balance system or that the balance is between 

 X-chromosomal female and autosomal male determiners, as in Dro- 

 sophila. In some dioecious plants, male determiners in the Y seem to 

 exist. We shall see later that the facts require a very different explana- 

 tion from that assigned to them and that they fit perfectly into the 

 point of view which we are developing here. There is also another 

 possibility, a plasmatic action of the M type, conditioned by auto- 

 somes or acting like a plasmon. (This will be discussed later for 

 certain examples in plants.) 



These primary conclusions are very different from those which 

 Correns originally drew for plants. He thought that in male hetero- 

 gamety, F is located in the X-chromosome and M in the Y-chromo- 

 some, M being epistatic to F. We have seen that this is impossible when 

 intersexuality is involved. Hartmann (1943), who tries in his book to 

 revive Correns' antiquated views in this and other respects, thinks that 

 they have been proved by the special conditions found in MeJondrium 

 (which will be discussed later). Actually, otherwise not a single well- 

 studied case of genetic intersexuality, including those in plants, can be 

 explained by the formulations of Correns. As the foregoing discussion 



