NOTES AND LITERATURE. 



GENERAL BIOLOGY. 



Mendelism and Cytology.^ — Guyer's doctor's thesis written in 

 1900 but printed and distributed in the latter half of 1903 is remark- 

 able for its "anticipation" of Mendel's law of purity of the germ 

 cells, the outcome, unlike Mendel's results, of a cytological study. 

 He first describes the course of spermatogenesis in normal pigeons. 

 The spermatogonia (the ancestral sperm cells immediately pre- 

 ceding the reduction stages) contain 16 chromosomes which are 

 split in the cell division that forms the primary spermatocyte. As 

 the primary spermatocyte grows, synapsis, or a fusion of the chromo- 

 somes in pairs, occurs ; and this Guyer interprets as the conjugation 

 of maternal and paternal chromosomes. Eight thick rings are formed 

 which break equatorially in the division by which the secondary 

 spermatocytes are produced. When the secondary spermatocytes 

 divide to form the young spermatozoa only four chromosomes are to 

 be seen. These chromosomes Guyer regards as quadrivalent and he 

 suggests that "reduction" takes place when they divide. 



He suggests that the reduction division of the four-fold chromo- 

 somes may be in any plane and so varying combinations of maternal 

 and paternal qualities will go to each spermatozoon. Thus it might 

 happen that in the division the maternal and paternal qualities were 

 segregated (and this he regards as the prevalent result in hybrids) ; 

 or it might happen that some of both the maternal and paternal 

 chromatin went to each spermatozoon. The "purpose" of the 

 formation of the quadrivalent chromosomes is to give greater 

 variability. 



In respect to hybrid pigeons, Guyer notes that the offspring of 

 the common brown ring dove mated with a white ring dove are 

 brown. The offspring of these brown hybrids are either white or 

 brown and the latter color predominates. The author says (p. 36) : 

 "This points to the conclusion that in the brown birds we may have 



plates. [Distributed (and printed ? ) 1903.] 



