Notes. 
665 
daughter-chromosomes as they approach the poles. Thus the reduc- 
tion in number is effected by an end-to-end fusion of the chromosomes, 
as Strasburger has already suggested. 
The next division by which the pollen-tetrads are formed takes 
place probably according to the normal karyokinesis in plant- cells, as 
it is found to do so in Lilium Martagon and L. chalcedonicum . In 
these two species not only were the slender chromosomes forming the 
equatorial plate observed, but also their longitudinal fission which is 
similar to that which takes place in vegetative cells. 
Before signs of approaching karyokinesis are apparent in the 
primary nucleus of the embryo-sac, fibres of great distinctness develop 
in the protoplasm of this cell, forming a spindle above and completely 
outside the nucleus, in position and appearance recalling Hermann's 
figure of the sperm-mother-cell of Salamandra maculata preparing 
for division (Archiv f. Mikrosk. Anat. 37). During division this 
nucleus behaves, so far as has been observed, with complete similarity 
to that of the pollen-mother-cells. In the later nuclear divisions in 
the embryo-sac, the doubling of the nuclear thread before the forma- 
tion of the chromosomes, and the fission in the nuclear plate into 
V-shaped daughter-chromosomes, were not to be observed ; in a few 
cases, however, the nuclear plate was seen to be composed of the 
humped chromosomes characteristic of the first division in this cell 
and in the pollen-mother-cells. But in the great majority of cases 
which were observed of these later divisions, the equatorial plate was 
formed of the usual slender bent chromosomes, which cleave longi- 
tudinally when in this position. Another point of interest connected 
with this embryo-sac is the fact that even without fertilization its central 
portion becomes occupied by a large number of nuclei. These 
nuclei arise by direct division and are formed as far as, at present, 
can be made out from the lower polar nucleus 1 . H. H. DIXON. 
Trinity College, Dublin. 
ABNORMAL NUCLEI IN THE ENDOSPERM OF FRITIL- 
LARIA IMPERIALIS. — In some material which was fixed during 
the spring of 1894, I have found some very peculiar forms of direct 
nuclear division, as well as intermediate forms between direct and 
indirect division. Nuclei before direct fission often attain monstrous 
1 Fuller details of this and the following note were laid before the Royal Irish 
Academy on Nov. n, 1895, and will be published with illustrations in their 
Proceedings, Vol. Ill, Pt. 4. 
