42 HEREDITARY CHARACTERS 



the reduction hi the number of the chromosomes takes place 

 in animals and plants. The larger number of observers state 

 that the loops which appear in the prophase of the reduction 

 division are formed by the union of two chromosomes 

 end-to-end. Shortly after the formation of the loops the 

 threads forming them split, but join up again into a single 

 thread before the nuclear membrane is disintegrated. This 

 splitting of the thread is supposed to foreshadow the longi- 

 tudinal splitting of the chromosomes in the next division. 

 The observers who maintain this view seem to offer the best 

 and most detailed evidence ; the researches of some of them 

 are the most recently published, and have been made with 

 full knowledge of the other interpretation. 1 A smaller 

 number of cytologists, mainly belonging to the school of 

 Louvain, state that what is interpreted by other observers 

 as a splitting of one thread, is actually an approxima- 

 tion of two threads, and that these two threads, which 

 join in a parallel manner, represent two chromosomes. 

 They maintain, therefore, that the loops are not formed of 

 two chromosomes joined end-to-end, but of two chromosomes 

 joined side by side. 2 A careful investigation of the pub- 



1 Arnold, G., "Ovigenesis and Sperniatogenesis of Planaria lactea," Archiv 

 fur Zellforschung, Hi., 1909; Farmer, J. B., and Moore, J. E. S., "On the 

 Meiotic Phase in Animals and Plants," Quarterly Journal of Microscopical 

 Science, xlviii., 1905; Fick, R., " Betrachtungen iiber die Chromosomen, ihre 

 Individualitat, Reduction, und Vererbung," Archiv filr Anatomic und Physio- 

 logic, Anat. Abt. Suppl. 1905; Goldschmidt, R., " Uber das Verhalten des 

 Chromatins bei der Ei-reifung und Befruchtung des Dicro coelium lancea turn, " 

 Archiv fur Zcllfoi-schung, i., 1908 ; Meves, F., " Spermatocytenteilungen bei der 

 Honigbiene," Archiv fur mikroskopische Anatomic, Ixx., 1907 ; " Es gibt keine- 

 parallele Konjugatiou der Chromosomen," Archiv fur Zellforschung, i. 4, 1908 ; 

 Montgomery, T. H., "The Heterotypic Maturation Mitosis in Amphibia," 

 Biological Bulletin, iv., 1903 ; Moore, J. E. S., and Walker, C. E., "The Meiotic 

 Process in Mammalia," Thomson- Yates Reports, University of Liverpool, 1905 ; 

 Otte, H., " Samenreifung und Samenbildung bei Locusta Viridissima," Zoolo- 

 yische Jahrliichcr, xxiv., 1907 ; Popoff, M., "Eibildung bei Paludina vivipara, 

 &c.," Archiv. fiir Mikroskopische Anatomic, Ixx., 1907 ; Schockaert, R., " L'ovi- 

 gdnese chez le Thysanozoon brocchi," La Cellule, xviii., xx., 1900, 1901 ; Tann- 

 reuther, G. W., "History of the Germ Cells and Early Embryology of certain 

 Aphids," Zoolorjische Jahruiichcr, xxiv., 1907. 



2 Gregoire, V., "La formation des gemini he'te'rotypiques dans les vcSge"- 

 taux," La Cellule, xxiv., 1907; Jannsens, F. A., "Evolution des Auxocytes 



