Studies on Chromosomes 97 



stand his conception, by the activation of the "latent" (not to be 

 confused with the " recessive") male possibility in the male pro- 

 ducing eggs. This is doubtless an admissible assumption, though 

 it seems to me to put a considerable strain upon the general 

 hypothesis. The more natural view would seem to be the one 

 directly suggested by the facts, i.e., that the parthenogenetic stem- 

 mother aphid is a heterozygote, the male tendency being in the 

 condition of a Mendelian recessive. But I will not enter upon a 

 discussion of this question, which is now in a condition where a 

 little observation and experiment will outweigh a large amount of 

 hypothesis. I think, however, that the first of the interpretations 

 that I suggested (following Castle) should not be rejected without 

 further data, and especially not until the question of selective 

 fertilization has been put to the test of direct experiment. 



Zoological Laboratory 

 Columbia University 

 February 13, 1908 



WORKS REFERRED TO 



BORING, ALICE M. '07 A Study of the Spermatogenesis of twenty-two Species of 



the Membracidae, Jassidae, Cercopidae and Fulgoridae. Journ. 



Exp. Zool., iv, 4. 

 CORRENS, C. '07 Die Bestimmung und Vererbung des Geschlechtes. Berlin, 



1907. Also (in abbreviated form) in Arch. f. Rassen- u. Ges.- 



Biologie, iv, 6. 

 DUBLIN, L. I. '05 The History of the Germ-cells in Pedicellina Americana. Ann. 



N. Y. Acad. Sci., xvi, i. 

 FOOT, K., and STROBELL, E. C. '073 The "Accessory Chromosome" of Anasa 



tristis. Biol. Bull., xii. 

 *O7b A Study of Chromosomes in the Spermatogenesis of Anasa tristis. 



Am. Journ. Anat., vii, 2. 

 GROSS, J. '04 Die Spermatogenese von Syromastes marginatus. Zool. Jahrb., 



Anat. u. Ontog., xx. 



'07 Die Spermatogenese von Pyrrochoris apterus. Ibid., xxiii. 

 HENKING, H. '91 Ueber Spermatogenese und deren Beziehung zur Eientwick- 



lung bei Pyrrorhoris apterus. Zeitschr. f. Wiss. Zool., li. 

 '92 Untersuchungen iiber die ersten Entwicklungs-vorgange in den 



Eiern der Insekten, 111. Ibid, liv, i. 



