I2O CHARLES V. MORRILL. 



or of the eggs does occur, not only in insects hut in at least two 

 other groups of animals and that it bears a definite relation to 

 sex-production. Whether the sexual tendencies are carried by 

 specific chromosomes or whether certain combinations of chromo- 

 somes cause one sex or the other to arise, is still an open question, 

 but that it is possible to demonstrate a nuclear difference in the 

 gametes, and frequently indeed, in the somatic tissues of the 

 two sexes, is now, I think, placed beyond doubt by many decisive 

 observations. 



April 27, 1910. 



LITERATURE. 

 Arnold, G. 



'08 The Nucleolus and Microchromosomes in the Spermatogenesis of Hydro- 



philus piceus (Linn.)- Arch. f. Zellf., II., i. 

 Baehr. W. B. von 



'07 Ueber die Zahl der Richtungskorper in parthenogenetisch sich entwickelnden 



Eiern von Bacillus rossii. Zool. Jahrb., Anat. u. Ontog., XXIV. 

 '08 Ueber die Bildung der Sexualzellen bei Aphididae. Zool. Anz.. 33. 

 '09 Die Oogenese bei einigen viviparen Aphicliden und die Spermatogenese 



von Aphis saliceti, u. s. w. Arch. f. Zellf., III., 2. 

 Baltzer. F. 



'09 Die chromosomen von Strongylocentrotus lividus und Echinus microtuber- 



culatus. Arch. f. Zellf., II. 

 Blochmann 



'87 Ueber die Richtungskorper bei Insekteneiern. Morph. Jahrb., XII. 

 Boveri, Th. (and Gulick. A.) 



'09 t'eber "Gcschlechtschromosomen" bei Nematoden. Arch. f. Zellf., IV., i. 

 Buchner. P. 



'09 Das accessorische Chromosom in Spermatogenese und Ovogenese der Or- 



thopteren, u. s. w., Arch. f. Zellf., III., 3. 

 Debaisieux, P. 



'09 Les debuts de 1'ovogenese dans le Dytiscus marginalis. La Cellule, Tome 



XXV. 

 Doncaster, L. 



'07 Gametogenesis and Fertilization in Nematus ribesii. Quart. Jour. Micr. 



Science, LI. 

 '10a Gametogenesis of the Sawfly, Nematus ribesii. A correction. Science, 



N. S., XXXI., February. 

 '106 Gametogenesis of the Gall-fly, Neuroterus lenticularis (Spathegaster 



baccarum). Part. I. Proc. Roy. Soc., B, Vol. 82. 

 Foot, K., and Strobell, E. C. 



'07<i The "Accessory Chromosome" of Anasa tristis. Biol. Bull., XII. 



'076 A study of the Chromosomes in the Spermatogenesis of Anasa tristis. 



Am. Jour. Anat., VII.. 2. 



'09 The Nucleoli in the Spermatocytes and Germinal Vesicles of Euschistus 

 variolarius. Biol. Bull., XVI., 5. 



