436 J. A. MURRAY, 



My statement that there are 48 pairs of sister-chromosomes rests on 

 many observations and partial counts of the daughter chromosomes in 

 the spermatogonium metakincses; and on an observation of a late 

 prophase in one of these cells. There were two radiations at nearly 

 opposite poles of the nucleus which (the nucleus) appeared in three 

 consecutive sections. The pairs of chromosomes were very closely 

 apposed and had apparently arisen by longitudinal splitting of single 

 elements. There were of these pairs between 40 and 50 in the three 

 sections. If this be so Lee has probably identified an amphiaster of 

 a spermatocyte II with little cytoplasm, with the spermatogonium- 

 amphiaster (cf. figs. 20 and 59). The growing zone is not represented 

 and there is no attempt to show how, from the telophases of spermato- 

 gonium mitoses (fig. 29), the resting spermatocytes are produced (fig. 30). 

 The gap is wide enough to need bridging. 



In chapter 2 the author discusses the structure and division of 

 the spermatocytes I. While dealing mainly with the evolution of the 

 chromosomes some points treated of in the present communication 

 are discussed. 



According to Lee the rings or ellipses, which are formed before 

 mitosis begins, lose the lumen and become solid unanalysable granules. 

 I feel sure if Lee had used material fixed with Perenyi's fluid he 

 would have had no difficulty in demonstrating rings even in the 

 equatorial plate. Osmic mixtures and sublimate produce images which, 

 however valuable for the study of the cytoplasm, are far from satis- 

 factory when the chromosomes are under observation. 



In the new paper also, Lee maintains his position with regard 

 to the existence of centrosomes. He confounds them with the peculiar 

 granules which occur scattered through the cytoplasm and are 

 characterised by a much stronger affinity for iron-alum haematoxylin 

 than is possessed by the centrosomes. The position, staining reactions, 

 and variations in size of the bodies which I have described as centro- 

 somes should leave no doubt in the mind of any one that here at 

 least Lee is at fault, A negative is proverbially hard to prove and 

 negative evidence in cases like the present is far from being con- 

 clusive. In view of these considerations Lee's account of the origin 

 of the achromatic figure loses considerably in probability and he 

 would probably find it difficult to account for appearances such as 

 my Fig. 14. There is moreover an important discrepancy between 

 the account of the prophases of mitosis of the spermatocytes I as 



