148 
Notes on Recent Literature. 
A further factor, which has undoubtedly been the source of 
much of the disagreement between the views of various writers, 
lies in the difficulty of seriation of the various stages. The main 
outlines of mitosis have been followed in the living cell, but for the 
details it is necessary to work with fixed material. In the earliest 
stages of the meiotic phase considerable growth in size of the nuclei 
takes place, but in the later stages this ceases and correct seriation 
can only be arrived at by close study of a very large number of 
preparations. It seems to be clear that stages which are looked 
upon by those who advocate the one view as being early, are placed 
later in the series by those who hold the alternative interpretation, 
and conversely. 
In a recent number of the Annals of Botany, Overton 1 has 
published a most interesting contribution to the subject. The 
additional evidence which he now brings forward certainly gives 
very strong support to the views put forward at an earlier time by 
him in conjunction with Strasburger, Allen and Miyake, 2 when the 
occurrence of a lateral pairing in the prophase of the heterotype 
division was advocated. 
As has been explained, the two threads which take part in this 
pairing are looked upon as respectively derived from the male and 
female gametes, which by their union gave rise to the zygote from 
which the plant has been developed. This being so, it would be 
natural to expect that in some species indications of the pairing of 
the threads might be found at an earlier stage in the life of the 
plant than that immediately prior to the formation of the germ-cells. 
Such cases would form a continuation of the series, which, starting 
for example with the Uredineae, where the two germ-nuclei remain 
quite distinct for the greater part of the life of the zygotic mycelium 
(2 X generation), includes forms like Cyclops and other Copepoda 
(in which, as Haecker and Reukert have shown, the maternal and 
paternal chromosomes form distinct groups, at any rate throughout 
the earlier mitoses of the individual), and has found its end terms 
in those numerous cases in which the union of the nuclei of the 
two germ-cells, at fertilization, is so close that, even in the first 
mitoses of the zygote, the maternal and paternal chromatin is already 
completely intermingled. Among such types as would be included 
under this last head, one might expect to find some in which the 
orderly pairing of the maternal and paternal chromatin does not 
take place until late in the life of the individual—not in fact until 
the onset of meiosis ; and others in which the orderly arrangement 
of the parental chromatin begins at an earlier stage in the life of 
the individual. In the latter case, such an arrangement might 
manifest itself through a tendency toward the association of the 
chromosomes in pairs in the dividing nuclei of the somatic cells, or 
through the existence of parallel paired threads in the resting nuclei. 
It may be said at once that the double structure shown by the 
primordia of the chromosomes, during the prophase of division in 
the pre-meiotic cells of the Cockroach, has been ascribed by Farmer 
1 “ On the Organisation of the Nuclei in Pollen Mother-cells of 
Certain Plants.” Ann. Bot., XXIII., 1909, p. 19. 
2 “ Histologische Beitriige zur Vererbungsfrage.” Jahrb. Wiss, 
Bot. XLII., 1905, p. 1. 
