May, 1906.] 
M Reducing Division in Ascaris. 
523 
tetrads arise by a conjugation of two longitudinally divided 
chromosomes, one of these maturation divisions is transverse 
and qualitive representing a true Reducing Division in Weis- 
man’s sense. There next arises the question as to which of the 
two divisions is the Reducing Division. This point the writer 
does not hesitate to say is very difficult, or perhaps incapable of 
complete demonstration in Ascaris. It has seemed to him that 
the presence of the Reducing Division was the all important fact 
and that the matter of deciding which division was qualitative 
was of much less importance. Because of this and because of 
the great difficulty of the matter I have not tried seriously to de- 
termine the question in the present investigation. The different 
chromatids in the tetrads are so similar and so difficult to find 
in favorable positions where all four of them can be seen at once 
that it is onlv with great reserve that statements as to the iden- 
tity and origin of the separate dyads of the first division can be 
made. But in this matter the angle between the tetrads may 
give a clue, not, however, in my judgment amounting to proof. 
By inspecting such stages a figs. 9 and 10 it will be seen that if 
Ave take the nearest common plane of the two tetrads, that in 
which the angle between them would lie, were it a plane angle 
(the plane of the paper in the cases cited) then we find that the 
equivalent chromatids arising by a split, lie perpendicular to that 
plane and the dissimilar chromatids arising bv a transverse break 
lie parallel to that plane. Applying this to fig. 12 in which the 
tetrads are oriented for the first division but not yet drawn out 
of their original angle we find that the first division would be the 
qualitative for it is the dissimilar dyads which lie on the different 
sides of the eauatorial plate of the spindle and Avill pass to the 
different cells in mitosis. 
The results given above were arrived at after examination 
of many hundreds of nuclei in the critical stages. The ones se- 
lected for the figures are unusual only in their clearness and in the 
favorable position of the parts. Of all the nuclei seen about 
half were so strongly contracted as to be impossible of resolution. 
Of the others all but two or three were clearly interpretable as 
stages in the process outlined above. A few, about 1-3 
per cent, should be interpreted either as products of folding or 
of a double longitudinal division. None were found which could 
be interpreted as products of the latter process Avhich did not 
lend themselves equally Avell to the other interpretation. 
Inasmuch as the results of the present investigation are 
diametrically opposed to those reached bv Brauer (2) on the sper- 
matogenesis of the same object, it might seem difficult to bring 
the observations of Brauer into harmony with those of the pre- 
sent writer. But such is not at all the case. One point which 
great stress upon and which is at first sight most con- 
vincing, is that the granules are sometimes clearlv doubly split 
at a very early period. A\ hatever the significance of this group- 
