80 BOTANICAL GAZETTE [januaby 



will be mentioned first. His view of the individuality of the chromosomes is based 

 quite largely on his well-known observations, and those of his pupils, on the resting 

 stage of the nucleus compared with the late telophase and early anaphases of 

 mitosis. The attempts of Fick,? Tellyesniczky, 8 and others to disprove indi- 

 viduality, come in for pointed criticism. Gregoire concludes that "II est certain 

 que les chromosomes persistent dans leur individualite, sous la forme de continus 

 structuraux, a travers toute Pontogenfese." Regarding reduction, he considers 

 it certain that the heterotypic mitosis dissociates the ft chromosomes, received 

 by the reproductive mother cells, into two groups of n/2; and probable that a 

 paternal chromosome always conjugates with a maternal of the same form. But 

 he finds nothing to prove that a pair of allelomorphic characters is fixed only in 

 one pair of chromosomes, nor that the chromosomes conjugated in the heterotypic 

 gemini are homologous maternal and paternal chromosomes. 



The hypotheses necessary to explain Mendelism on a cytological basis are 

 given as follows: (1) The chromosomes play a preponderant role in the trans- 

 mission and determination of hereditary characters. (2) The different chromo- 

 somes of a given cell are bearers of different properties. (3) In the chromosomes 

 of a hybrid egg a Mendelizing character is represented only by two chromosomes, 

 one maternal, one paternal. In one of these the character is represented in a 

 recessive condition (modalite* recessive), in the other in the dominant condition. 



It must be said (and Gregoire would probably agree with this) that the con- 

 ception of representative particles in the dominant and recessive condition merely 

 projects the phenomena of dominance back into the germ cell without attempting 

 an analysis of its meaning, or how it comes about, and hence explains nothing. 



This appears to the reviewer to be a serious and probably fatal objection to the 

 last hypothesis. 



On the basis of these hypotheses the germ cells would receive of each pair a 

 single recessive chromosome (maternal or paternal) and a single dominant chromo- 

 some (maternal or paternal). In the prophase of the heterotypic _ 

 chromosomes join in pairs, and observation favors the view that these are homolo- 

 gous maternal and paternal chromosomes. Then after reduction half the germ 

 cells would receive a "dominant" chromosome, and half the corresponding "re- 

 cessive" chromosome. We thus arrive at Mendel's conception, and the chances 

 of meeting he described between germ cells are here conceived between chromo- 



Granting the three hypotheses then, Mendelian phenomena would be 

 expected to result. 



In Pisum eleven or more pairs of allelomorphs have been observed and the 

 red uced num ber of chromosomes is only seven; which shows that in this case, at 



7 J ICK > Betrachtungen uber die Chromosomen, ihr Individuality, Reduktion 

 und Vererbung. His-Waldeyer's Archiv. 1906; Vererbungsfragen, Reduktions- und 

 Chromosomenhypothesen, Bastard-Regeln. Engeb. Anat. Ent. 1907. 



« Tellyesniczky Zur Kritik der Kernstrukturen. Archiv. Mikr. Anat. 60: 

 68^06. x 9 o 2 ; Ruhekern und Mitose. Idem 66:367-433. 1905. 



mitosis 



somes. 



