The determination of sex ia animal development. 745 



Were there not in plants — as in animals — dioecious, as well 

 as henuaphrodite, species, the differentiation of two sorts of gametes 

 might suffice. The equivalents of male- and female-eggs ^) would, 

 however, appear to be here also necessary. If my reading of the 

 signs be not erroneous, they go to show the difiereutiation and 

 determination of sex in plants as happening at the formation of 

 spore-raother-cells. As elsewhere shown, the primary germ-cells of 

 animals represent the spore-mother-cells of the Metaphyta. Possibly 

 the determination of sex originally took place at the first division of 

 the former, that is to say, before the Metazoan sexual generation 

 attained any high degree of organisation. Nay, possibly there may 

 still be lowly animals, in which the division of the primary germ- 

 cells into secondary ones at the same time furnishes the determination 

 of sex. 



Should it turn out to be the case, that the spore-mother-cells 

 were concerned in the determination of sex, this latter would be in 

 connection with the reduction of chromosomes in both animals and 

 plants, 



VII. Significance of the Reduction of Chromosomes. 



Finally, the question as to what relation may subsist between 

 the reduction of chromosomes and the determination of sex suggests 

 itself for consideration. Like Strasburger (1. c. p. 769), but in- 

 dependently of him and from different facts and considerations, I 

 arrive at the conclusion of a close connection between the two. 



1) From the exceedingly interesting experiments of Gregor Mendel 

 on hybridism between green and yellow peas, cited by Strasburger 

 on p. 767, the existence of four sorts of gametes appears to be here 

 indicated. Indeed, Menbel drew this conclusion, for in his opinion his 

 results pointed to the occurrence of two sorts of male and of female 

 "Befruchtungszellen". In this inter- crossing the yellow is dominant or 

 pre-potent. This manifests itself after the first generation. If such 

 hybrids be fertilised with their own pollen, in the seed-pods there are 

 on the average 3 yellow peas for each one of a green colour. How 

 this serves to indicate the existence of four kinds of gametes may be 

 gathered from Strasburger's memoir. The case, however, is one of 

 hybridism with self-fertilising hermaphroditism, and the four sorts of 

 gametes, if present, would not be sexually differentiated like those 

 of animals. Vide: Gtregor Mendel, Versuche über Pflanzenhybriden, in: 

 Ostwald's Klassiker d. exacten Wissenschaften, No. 121. See also 

 Bateson's translation in: J. Roy. hortic. Soc, V. 26, 1901. 



