SYNAPSIS IN THE EGG OF THE WHITE RAT 455 



threads in the remainder of the nuclei, point to this conclusion. 

 Such a phenomenon has been elaborated upon by McGill in the 

 case of the Dragonfly (McGill, '06), and has been described by 

 numerous other authors. 



In regard to those questions which attracted attention in the 

 first place, it seems: (1) There is no evidence, during the period 

 of synapsis, of the presence of an accessory chromosome or sex 

 chromosome. (2) If it be assumed that the individual leptotene 

 threads represent chromosomes, chromosomes seem to pair dur- 

 ing synapsis; and this is a side by side pairing, or parasynapsis. 

 (3) Under this same assumption, it would seem that individual 

 chromosomes maintain their identity throughout this period up 

 to and including the diplotene stage, although there is oppor- 

 tunity for mixture of material in the chromatic enlargements 

 during the pachytene stage. There is, however, no satisfactory 

 evidence that these individual leptotene threads do represent 

 chromosomes. 



LITERATURE CITED 



Arnold, Geo. 1908 The prophase in the ovogenesis of Planaria lactea. Arch. 



f. Zellforsch, Bd. 3. 

 Browne, E. N. 1910 The relation between chromosome number and species in 



Notonecta. Biol. Bull., vol. 20. 

 Cardiff, I. D. 1906 A study of synapsis and reduction. Bull. Torrey Botan. 



Club, vol. 33. 

 Davis, H. S. 1908 Spermatogenesis in the Acrididae and Locustidae. Bull. 



Mus. Comp. ZooL, vol. 53. 

 DuESBURG, Jules 1908 Les Divisions des Spermatocytes chez le Rat. Arch. 



f. Zellforsch., Bd. 1, pp. 399-449. 

 Foot, K. and Strobell, E. C. 1910 Pseudo-reduction in the oogenesis of 



Allobophora foetida. Arch. f. Zellforsch., Bd. 5. 

 Von Hoof, Lucien 1912 La spermatogenese dans les mammiferes. La Cellule, 



T. 27. 

 Jordan, H. E. 1911 The spermatogenesis of the opossum, Didelphys virginica, 



with special reference to the accessory chromosome and the chondrio- 



somes. Arch. f. Zellsforsch., Bd. 7. 

 King, Helen D. 1908 The oogenesis of Bufo lentiginosis. Jour. Morph., 



vol. 19. 

 Long, J. A. 1912 The living eggs of rats and mice. Univ. of Calif. Pub. 



ZooL, vol. 9, no. 3. 

 McGill, Caroline 1906 Behavior of the nucleoli during the oogenesis of the 



dragonfly with especial reference to synapsis. Zool. Jahrb. Abt. Anat., 



Bd. 23. 



