338 SYDNEY J. HICKSON. 



and referring to Plate's own figure, pi. vi, fig. 17, as afford- 

 ing a convincing proof ofit. Neifclier Bntschli (1), Wrzesni- 

 owski (27), nor Schneider (24) appear to have observed them, 

 and Sand (23) only mentions one '^ centrosome " as being 

 present in this genus. 



The number of raicronuclei in Dendrocometes varies, but, 

 as stated above, the usual number is three. In individuals 

 that are neither conjugating nor preparing for gemmation it 

 is sometimes difficult to count the micronuclei, as they are 

 very small, and are difficult to distinguish from other bodies 

 in the cytoplasm which have affinities for the stains that are 

 used. However, a certain number of individuals with 

 moderately clear cytoplasm can nearly always be found, and 

 in these it is not difficult to recognise the micronuclei in sec- 

 tions stained by the irou-hfematoxylin and iron-brazilin 

 methods (13). There are sometimes two micronuclei, and 

 sometimes four, and but rarely five. I do not believe that 

 thei'e are ever more than five or less than two. 



In the state of rest the micronucleus consists of a small, 

 irregular granule of chromatin, enclosed in a clear zone, 

 which is invariably perfectly spherical in shape. There is no 

 evidence of a definite membrane surrounding the clear zone. 

 The zone is from 2 — 4 ju in diameter. It is very difficult to 

 form an opinion of the nature of the substance composing the 

 clear zone. When the nucleus is in a state of rest this zone 

 resists the action of all the stains I have tried, and no lines 

 nor granules of any kind or description can be seen in it. It 

 is possible that it may be a mere artefact, due to the shrinkage 

 of the chromatin during the process of preservation, but the 

 regularity of its shape and its relation to the chromatin 

 granule do not support this view. In my opinion it really 

 represents the '^ achromatin " elements of the nucleus. 



When preparing for division the micronuclei increase con- 

 siderably in size, the solid granule of chromatin becoming 

 converted into a 'coarse skein (PI. 18, fig. 14m). Later the 

 skein breaks up into a much finer tangle (PI. 17, fig. 3), which 

 gradually fills up nearly the whole of the clear zone. In 



