N. M. STEVENS. 



\\"'TC it not for a few >t~ condensation of an apparently 



equal pair of heterochromosomes in the male germ cells (Lepidop- 

 tera, Stevens, '06, Pederer, '07, Cook, '10; Anisolnlxi maritinni, 

 Randolph, '08), and in the female- germ cells (Aphrophora, 

 Stevens, '06, Rhabditis ni^ron-nosu, Bnveri, 'ii>, one misjit sus- 

 pect that the condensed condition of the odd chromosome and 

 the unequally paired heterochromosome of tin- growth stage of 

 the first spermatocytes might be due to their unpaiied or 

 unequally paired condition preventing them from joining with 

 the other bivalent chromosomes to form a spireme, especially 

 in cases of parasynapsis. In Cuh'.v no such difference is effect- 

 ive in bringing about a condensed condition of one pair of 

 chromosomes and in Anopheles, where the difference in size of 

 the heterochromosomes is slight, condensation is much less 

 complete than in most cases. In the guinea-pig condensation 

 is complete from the synapsis stage on. 



In the guinea-pig the condensation of the heterochromosome 

 pair and its behavior in mitosis are as typical as in Tenebrio 

 and many other coleoptera previously described by the author, 

 and only the large number of chromosomes of such a consistency 

 that good fixation in mitosis is difficult to secure, makes it 

 impossible to give as complete a demonstration of the relation 

 of the heterochromosomes to sex as in many other forms. 



BRYN MA\VR COLLEGE, 

 May 23, 1911. 



LITERATURE CITED. 

 Boveri, Th. 



'n L'ber das verhalten der Geschlcchtschromosomen bei Hermaphroditismus. 

 Beobachungen an Rhabditis migrovenosa. Yerhandl. d. IMiys.-Mrd. 

 Gesellschaft zu Wurzburt'. N. F., XLI. 

 Cook, M. H. 



'10 Spcrmatogenesis in Lepidoptera. Proc. Phila. Acad. Sri.. April. 1910. 

 Dederer, P. H. 



'07 Spermatogcnesis in Philosamia cynthia. Hull. Biol., XIII. 

 Guyer, 



'09 The Spermatogenesis of the Domestic Guinea (.Xiimidia mrlra.uii- d'un.). 



Anat. Anz., XXXIV., Xo. 20, 21. 

 '09 The Spermatogenesis of the Domestic Chicken (Gallu< uallu- ilom.). Ibid., 



No. 22, 24. 



'10 Accessory Chromosomes in Man. Biol. Hull . XIX. 

 Jordan, H. E. 



'n The Spermatogenesis of the Opossum. Ea-'> m / I >< 



