710 Proceedings of the Royal Irish Academy. 



from two to three nucleoli present. The next stage entered into by 

 the nucleus is that which is conveniently called the " synaptic" stage 

 by Moore ^ in which the linin aggregates together into a spherical mass 

 in the nuclear cavity drawing with it the chromatin granules. To judge 

 from the precision and clearness of the nuclear figures in surrounding 

 tissues of preparations containing the nuclei of the pollen mother- cells 

 in "synapsis," we may infer with the last-mentioned writer and 

 Farmer that this appearance is not due to defective fixing ; although 

 it is quite conceiveable that methods which are adequate to fix the 

 other nuclei are not suitable for these nuclei in this particular stage. 

 The spherical mass, formed in the synaptic nucleus appears to be a 

 ball formed of an extremely closely wound-up delicate thread. The 

 thread is beaded with very minute chromatin granules. In some cases 

 a looped portion of the delicate thread is not wound into the mass but 

 extends from it to the nuclear membrane. Again, in some cells a 

 number of granules (six to twelve) instead of the single mass are to be 

 observed, formed by the nuclear thread. I have not been able to 

 discover whether this latter appearance is a definite stage occurring in 

 all the pollen mother-cells or whether it represents a state which may 

 occasionally replace the more general condition. 



In the next stage I observed the nuclear thread had the form of a 

 loosely coiled skein. It was still very delicate. In numerous places 

 along the thread portions were so folded on each other as to lie for some 

 distance parallel to one another (fig. 2) ; this appearance is not probably 

 due to the fission of a single thread, but rather to the approximation of 

 two distinct portions, as may be concluded from the occasional wide 

 separations and crossings of the parts of the thread, as well as from the 

 fact that the approximated portions come to lie more nearly parallel to 

 one another in the latter stages- (fig. 3.) This coiled thread next 

 breaks into a number of portions consisting of two more or less parallel 

 and comparatively long portions, which certainly, by their appearance, 

 suggest the idea that each pair has arisen by the approximation of two 

 thread-like portions rather than by the cleavage of one thread (fig. 5). 

 Sometimes one may lie across the other or may be bent so as to cross 

 it twice or three times, or again, the two may be united by one pair of 

 ends while the other ends diverge from one another. At this time 



' Ann. of Bot., vol. ix., p. 431, September, 1895. 



^ Farmer (Ann. of Botany, September, 1895) calls attention to a similar 

 appearance in the nuclei of the Liverworts, but concludes that it is brought about 

 by fission. 



