Chromatin as "'Hercditarij Substance'' 353 



gall flies and ])hylloxeran,s.* And observations have \n{v\\ 

 been published which strono-ly indicate the dependence of 

 sex upon chromosomes in other animals in which partheno- 

 genesis and hermaphroditism occur. This is notahlv true 

 of aphids, certain nematode worms, and a pteiopod mol- 

 lusc. Summing up, we may say, then, that in a considerable 

 i:jumber of animals sex is proved to l)e hereditarv and to be 

 connected with the chromosomal conchtion of the germ- 

 cells. 



The Connection of Mutation mith Particnhir Chroinosnmes 



Finally, the most surprising evidence in favor of the 

 theory that chromosomes are bearers of heredity, is the dis- 

 covery that certain attributes in some animals and jjlants, 

 not necessarily peculiar to either one sex or the other, but 

 which arise as mutations and are transmitted in Meiidelian 

 fashion, are connected with particular chromosomes. The 

 best investigated examples are furnished hy the evening 

 primroses, plants which have become famous in connection 

 with the mutation theory. 



Mr. R. Ruggles Gates, one of the foremost workers in this 

 specialty, has lately epitomized the facts and views held icla- 

 tive to the chromosomal characters of j)hints. He writes 



* The investigators who have coniribiitcd most l<i llic (hscriptions of 

 the chromosomal conditions of the honey bee are .] . V. Meves {Die 

 8p€vmatociiten1eUun(i€n bei der Iloiiif/bieue, Areli. f. Mikr. Anat. Bd. 70, 

 p. 414, 1907) and H. Nachtsheini, referred to above. Meves and J. 

 Deusberg (Die SpermaioryienteihiiKfeii bei der //or«j,v.v/'. Areh. fiir 

 Mikr. Anat. Bd. 71, 1908)' have investigated the wasp. The gall flics 

 have been studied y)y !>. Doncaster. {Gameiotieneaiit of the Gall fly 

 Neuropterus i.ENTicuLARis Proc. Bov. Soc. B. 8:2, 1910, p. 88 and B. 83, 

 1911, p. 47().) The germ-cells of certain Phylloxerans have 

 been the subject during the last ten years of some of T. H. Morgan's 

 most important studies. His first paper, {The ^Inle and Female Eggs 

 of PhyUoxerans of the Hickories, Biol. Bull. Vol. 10, ]>. 210) was 

 published in 1900. In all he has written something like a dozen 

 papers on the subject, the last so far as T know having app<'Mrc(l in 1915 

 {The Predetermination of Sex in Phylloxerantt and Aphids. Jour. Kxper. 

 Zool. Vol. 19, Oct. 1915, p. 385). 



