Heterotype Karyokinesis and its Significance. 29 
HETEROTYPE KARYOKINESIS AND ITS SIGNIFICANCE. 
T the meeting of the Royal Society held on December 10th 
last, Professor Farmer presented some of the results of 
work carried out by him, in conjunction with Mr, J. E. S. Moore 
and Mr. C. E. Walker, on certain points in the cytology of malignant 
tumours (or what are known in common talk as “cancer”). The 
main discovery involved has the widest bearings, and if well-founded 
(as there is every reason to believe) will, we may hope, form the 
starting-point of new lines of progress in biological science. It is 
in fact one of the most important discoveries that has been made 
since the modern study of cytology came into existence not much 
more than thirty years ago, and forms a kind of turning-point, at 
once completing the series of leading facts concerning nuclear 
division which we owe to the distinguished cytologists of the last 
three decades, and opening a fresh chapter in the history of cyto— 
physiological knowledge. We make no apology, therefore, for the 
present notice, though the work in question is not strictly botanical. 
The main facts of “heterotype” karyokinesis will be within the 
knowledge of all botanists who have followed the recent progress 
of cytological research ; but without going into the history of the 
subject it may not be out of place to recapitulate them briefly here 
The essential points distinguishing the heterotype form cf nuclear 
division from the ordinary homotype (somatic) form occurring in 
the cells of the bodies of all animals and plants may be given under 
four heads:— 
(i.) The cell in which the heterotype division is going to occur 
passes through a phase of rest and growth accompanied by certain 
changes in the chromatin of the nucleus. 
(ii.) The chromosomes, or rod-like bodies into which the chro¬ 
matin net-work of the nucleus is resolved at the onset of nuclear 
division appear in half the number characteristic of all the preceding, 
somatic divisions. 
(iii.) The chromosomes are strikingly different in shape from 
those seen in the somatic divisions. Instead of having the form of 
V-shaped rods, they are seen as loops or rings or various modifications,, 
and lie longitudinally on the threads of the achromatic spindle. 
(iv.) The division of the chromosomes, which in somatic 
karyokinesis takes place by means of a longitudinal splitting,. 
