12 
themselves however, are also sometimes different and 
perhaps not always complete. Also the fixing agent and 
the method of investigation may contribute to the diver- 
gence between the results of different investigators. 
Escoyez, for example, observed a perinucleolar cavity, 
whilst Î, using an other method of fixation observed no 
such cavity. Miss Merriman and Escoyez both believe 
they have seen ring-shaped nuclear-plates, whilst | came 
to a different conclusion, using a method by which the 
nuclear-plates could be observed edgeways as well as 
sideways. 
It seems to me desirable that the various investigators 
should endeavour to complete their observations on 
Zygnema, and extend them to more species and also 
should apply different methods of investigation. Exchange 
of material might also be very useful. Some such action 
would be conducive to agreement, which will not be 
readily obtained by other means. 
EXPLANATION ON FIGURES. 
Fig. 1. The resting nucleus. 
» 2. Nucleoli isolated by the use of chromic acid. 
» 3. Nucleolus-thread with the rest of the nuclear 
network. 
» 4. Nucleolus-thread isolated by the use of chromic 
acid. 
» >. Karyokinetic figure; the nucleolus has dissolved; 
threads are formed resembling strings of pearls. 
» 6. Nuclear-spindle with the nuclear-plate. 
» 7. Nuclear-plate isolated by the use of chromic 
acid. 
