in Pinus and Thuja. 549 
chromosomes persist in the reticulum of the resting nucleus in the form of 
bodies with projecting processes. 
The majority of investigators since the time of Rabl, while contending 
for the truth of the general hypothesis set forth, have failed to recognize 
anything comparable with the chromosomes in resting nuclei. Recently, 
however, Rosenberg (‘04) and Overton (’05) have asserted that in certain 
genera it is possible to recognize in the resting stage of the nucleus a number 
of chromatic lumps which is equivalent to the number of somatic chromo- 
somes typical of the species. For these lumps Overton (’04) has suggested 
the name prochromosomes. As already stated above it is not disputed 
that the chromosomes may for a time persist as rather large irregular lumps, 
but it seems quite probable that such appearances are due rather to growth 
conditions than that they represent a condition which has any great 
significance from the standpoint of heredity. For is it not true that, in at 
least the great majority of forms of both plant and animal so far thoroughly 
investigated, all vestiges of the structure of the chromosomes of the pre- 
ceding generations are lost ? The term prochromosomes, as applied to the 
chromatic lumps of the resting nucleus, is open to certain objections which 
are well founded. In all of the forms which Overton himself cites, it appears 
that the identity of these bodies is completely lost before final chromosome 
development takes place, so that it cannot be definitely stated that these 
bodies represent structures which are even approximately the same as the 
chromosomes of this division, as the name would imply. 
In the case of P odophyllum^ Overton (’05) says : ‘ Doch die Hauptsache 
ist, dass auch hier, gerade so wie bei den andern Pflanzen, Linin und 
Chromatinstruktur parallel zu liegen kommen \ And this, if it be true, 
relegates the entire speculation concerning prochromosomes to a position 
of minor importance. 
This statement brings us also to a consideration regarding the origin of 
chromosomes from the spirem, concerning which there is a wider diversity 
of opinion than for any other stage of mitosis. It is maintained by one 
group of investigators, among whom Strasburger, Guignard, Berghs, Allen, 
Overton, and others are prominent, that the chromatin of the resting nucleus 
exists in a state of complete segregation, and that previous to synapsis, the 
maternal and paternal each arranges itself into a continuous spirem. These 
two spirems, lying close to each other, become arranged parallel through- 
out, approach very close together, and apparently fuse side by side. This 
fusion takes place during the synaptic phase. Following synapsis the 
spirems again separate to a greater or less degree, and segment transversely 
to form the bivalent chromosomes. Each part of a bivalent is therefore 
derived purely from the maternal or paternal ancestry. The other view 
which opposes this conception, and which has been supported by Farmer 
and Moore, Mottier, Schaffner, Juel, and others, denies the presence of two 
