716 Proceedings of the Royal Irish Academy. 



fig. of Sperm-motlier-cell of Salamand/ra maculata, preparing for 

 division (ArcMv f. mikros. Anat. 37). I liave figured somewhat similar 

 spindles in the oosphere of Pinus silvestris (Ann. of Eot., 1894). 

 The presence of this spindle seems to be constant, for it occurred in 

 every embryo-sac of a yonng ovary examined by means of a series of 

 sections, and in other ovaries at the same stage of development. 

 Sometimes, however, when the nucleus has approached the distal end 

 of the cell, the spindle lies beneath it. This spindle is also to be seen 

 in embryo- sacs of the same stage in L. Martagon. I have not observed 

 the fate of this spindle. The nuclear filament of the primary nucleus 

 of the embryo-sac, before the individual chromosomes can be distin- 

 guished, resembles that of the pollen -mother-cells; it is delicate and 

 complexly coiled, and often two portions of the thread run parallel to 

 one another for some length. After the chromosomes have become 

 separate from one another, each is seen just as in the pollen-mother- 

 cells to be composed of two longitudinal portions, lying more or less 

 closely in apposition to one another, but often bent across one another, 

 or forming a loop together. The nuclear plate is formed of short thick 

 T-shaped chromosomes, like those of the pollen-mother-cells. I did 

 not observe the complete division of these, and the formation of the 

 diaster, but owing to the similarity of the earlier stages, and the form- 

 ation of the nuclear plate with these stages in the nuclei of the pollen 

 mother-cells, we may conclude with probability that the later processes 

 are similar. 



In the short stages of rest preceding the next divisions of the 

 nuclei of the embryo-sac I have never seen the nuclei in " synapsis," 

 nor have I seen any of the other phenomena which are characteristic 

 of the first division of the primary nucleus, and of the nucleus of the 

 pollen mother-cells, in the divisions of the lower groups of nuclei in 

 the embryo-sac. These characteristics, i.e.^ doubling of the thread, 

 before the formation of the nuclear plate and fission into V-shaped 

 daughter chromosomes, are not, as a rule, to be observed in the 

 divisions ocurring in the upper group, although, in two cases, I have 

 seen the equatorial plate, formed of humped chromosomes, in the first 

 division, taking place at the upper end. In the great majority of 

 cases the plate is formed, even in this division, of slender bent 

 chromosomes, and in all the other divisions this latter form obtains 

 (figs. 16 and 17). 



It may be seen that these observations do not lend support to the 

 assumption that the so-called " division with reduction " takes place 

 either in the formation of the nucleus of the pollen grains, or in the 



