570 REPORT—1905 
germ-plasms, and therefore Weissman predicted that a transverse division of the 
chromosomes would be found to take place by which the reduction would be 
brought about. This was soon discovered to be the case for many animal 
cells, the reducing division taking place during the formation of the sexual cells, 
but in plants this was not so easily determined. Belajeff, Dixon, Atkinson, and 
others maintained that a true reduction division took place in the cases examined 
by them ; but the majority of observers, Miss Ethel Sargant, Strasburger, Farmer, 
Mottier, and many others, maintained that there was no transverse division, but 
that all the divisions were longitudinal. Recently, however, Farmer and Moore 
have reinvestigated the whole sequence of events in both animals and plants, with 
the result that a true reduction division is found to occur in the heterotype stage. 
In many investigations which have recently appeared this transverse division is 
confirmed, but the exact details of the process are not yet agreed upon. Farmer and 
Moore state that the spireme thread first becomes longitudinally split, the two 
longitudinal halves then fuse again, and subsequently bivalent chromosome loops 
are formed which divide transversely in the middle, and so produce two monovalent 
chromosomes which pass to opposite poles of the spindle, as already described. 
Gregoire, on the other hand, states that the threads at the first sinapsis become 
approximated together and then fuse ; the double thread thus produced breaks up 
into chromosomes, which are thus bivalent in a different sense from those of 
Farmer and Moore, the monovalent chromosomes being produced by a longitudinal 
splitting of the thread, which divides it into the two original halves which fused 
together. 
Which of these two methods will ultimately be found to be the correct one 
remains to be seen, but Allen has recently published an account of the process as 
it occurs in Liliwm canadense, in which he agrees substantially with Gregoire, 
and states definitely that the first appearance of the double nature of the thread 
is not due to a longitudinal splitting of a single thread, but to an approximation 
of two threads, which ultimately fuse together to form a single continuous thread 
in the nuclear cavity. This thread at a later stage undergoes a longitudinal 
splitting, possibly into those which formerly united; but this is not certain. The 
double thread then divides up into segments, the chromosomes, and in the sub- 
sequent series of events the longitudinal halves of these chromosomes become 
distributed to the opposite poles of the spindle. Each chromosome is thus seen to 
be bivalent; but whether each half of the chromosome is to be regarded as a 
monovalent chromosome is doubtful, as the fusion of the original threads was 
complete, and there is no means of deciding as to how far the subsequent longi- 
tudinal division of the completely fused thread separated it into its two original 
arts, 
: Allen expresses the opinion that the characteristic peculiarities of the hetero- 
type division are due to the formation of two distinct spirems, which contain the 
substances derived respectively from the male and female parents. The two 
spirems fuse together into a single thread in the sinaptic stage, and thus bring 
about an intimate association of the male and female hereditary substances which 
were brought together by the fusion of the germ-cells thousands of cell generations 
previously, 
This view is, of course, so totally different from that of Farmer and Moore, 
Strasburger, and others, that further investigation is necessary before we can 
come to any precise conclusion concerning the nature of the heterotypical 
division. Allen’s suggestion opens up an extremely interesting problem in 
cytology, and one which is intimately bound up with recent views on heredity. 
Sinapsis. 
The term ‘sinapsis ’ was first given by Moore to that stage in the prophases of 
the nuclear division of the sexual cells in which the contraction of the nuclear 
thread around the nucleolus at one side of the cavity of the nucleus takes place. 
If this phenomenon’ is not a result of the action of the fixing reagents, then it 
indicates some striking change in the metabolic activity of the nucleus, This 
