236 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VoL. 11. 



a quantity of haematogen as definitely as it has unmodified chromatin. 

 This hsematogen plays no part at all in the division, and when the power 

 of division is lost or greatly diminished the unmodified chromatin is 

 confined in the nuclear membrane and the terra-cotta-red stain in the 

 cell body gives place to that characteristic of haemoglobin. 



It has been already observed by Flemming* that chromatin is very 

 abundant in dividing haematoblasts, and he compares this great volume 

 with that of the same substance in the fully formed red cells.f He also 

 speculates on the cause of the increase in the quantity of chromatin and 

 mentions two possible explanations: either the stainable substance is 

 taken fromthe protoplasm of the disc into the nucleus or the nuclei of 

 the red cells contain chromatin in a greatly condensed, form so when that 

 division commences it suffices to fill out the enlarged nuclear figure. 

 He, apparently, inclines to the latter view because the nuclei of fully 

 formed red cells stain more deeply than do those of other cells, yet 

 expresses himself as not quite certain that a portion of the protoplasm 

 of the disc does not go into the nuclear figure in division. Strasburger^ 

 adopts the second explanation. Flemming§ further states that the 

 mitotic figure in the haematoblasts is 2 — 3 times greater than the nucleus 

 of the resting or fully formed cell. 



Flemming's observation as to the great amount of chromatin present 

 in the haematoblast is correct, but he has used a wrong or incorrect 

 standard when he selected the nucleus of the resting red cell. I have 

 already pointed out that there are two kinds of chromatin in the 

 latter. The network chromatin is never reinforced by that in the 

 spaces of the network and it alone is a direct descendant of the mitotic 

 chromatin of the haematoblast. This is very clearly shown by haema- 

 toblasts one of which is represented in Fig. 14. Now the original chromatin 

 of the haematoblasts is from the time of their differentiation as such 

 specially abundant. The quantity of this substance is from this time on 

 to that of the formation of the red cells so great that the haema- 

 toblast seems hardly capable of containing much else, and, as a con- 

 sequence, divisions appear so rapidly that I have never yet succeeded in 

 observing the resting stage and the same has been the experience of 

 other observers. There is in this, plainly, a reason for a degeneration of 

 part of the chromatin into the eosinophilous substance already described. 



* Zellsubstanz Kern-und Zelltheilung, p. 262-3. 



+ The two upper cells represented in his fig. T. p. 263, op. cit., are fully developed blood 

 cells. 



J Zellbildung und Zelltheilung, l88o, p. 330. 

 § Arch, fiir Mikr. Anat., Bd. XVI, p. 396. 



