580 MR. W. C. WORSDELL ON THE DEVELOPMENT 
lying in a different plane, this nucleus is frequently cut away in 
sections which show the synergide. In the majority of cases 
there were also two additional nuclei shown lying either in close 
proximity to each other or separated by a little space, each being 
equal in size to the nucleus just described. These are the two 
polar nuclei. In position they were either quite close to the 
egg-apparatus or some distance away from it (Pls. XX., XXI. 
figs. 14-17, 19, 205, pn). Very various were the positions 
observed to be taken up by these two nuclei with regard to each 
other. Most frequently they might be seen in close connexion, 
and this connexion was observed, in a transitional series of cases 
to result from, at first, a slight contact at one point to the most 
complete fusion, during which the common wall of the two nuclei 
gradually became absorbed, the two nucleoli fused into one, and 
a single deep-coloured and very conspicuous nucleus was formed, 
double the size of the two original ones. This is the secondary 
or definitive nucleus (figs. 18, 21, 22, da). 
In a few instances a deep-coloured elongated mass, which may 
possibly represent part of a pollen-tube, appeared above or 
between the two synergide (figs. 19, 21, pt). 
As regards the chalazal end of the embryo-sac at this stage of 
the development, in the rare cases where it was clearly exposed 
to view three distinet antipodal cells were seen to be present 
(figs. 14 & 15, ant). Two of these, lying side by side and occu- 
pying the extremity of the sac, were slightly elongated, and in 
shape rather like the synergide, but in size they were very much 
smaller than the latter. The third cell, somewhat similar in shape 
to the ovum, lay in contact with their upper ends. Very often 
but two antipodal cells were visible. Owing to the obliquely 
lying position of the ovules in the ovary, the embryo-sac was 
but rarely cut medianly through from one end to the other, and 
thus usually the micropylar end was seen in one section, and the 
antipodal end in another section of the same ovule. Fig. 14, 
however, was made from a single section. At a certain stage in 
the development of the ovule, of which much fewer preparations 
were obtained, the ovum begins to form the young embryo. 
At the youngest stage the latter resembles somewhat one of the 
synergidz, at whose side it grew out as an elongated cell, 
swollen at its anterior end, and tapering at the other by a very 
narrow prolongation towards the micropylar region. It could 
