No. 466.] STUDIES ON PLANT CELL.— VIII. 709 
logical independence of the chromosomes. Miss Merriman 
reports the origin of the nucleoli as masses among the meshes 
of chromatin from which they draw their substance. Mano, in 
contrast to Wager, holds that the nucleoli appear as globules 
independent of the chromatin network and later flow together 
into a single body. The chromosomes are also believed by 
Mano to be morphologically independent of the nucleolus and 
if the latter furnishes material to the former it is not by the 
emergence of strands as described by Wager. Mano then holds 
the nucleolus to be an accessory structure without morphologi- 
cal relation.to the chromosomes. 
The theory of the individuality of the chromosomes is of 
course vitally concerned with the problem of the morphology of 
the nucleolus but this topic we have reserved for later treatment 
under the caption : * The Essential Structures of the Plant Cell 
and their Behavior in Ontogeny.” Tke- chromatin and nucleoli 
within the nucleus of a higher plant lie in a vacuole whose fluid 
content is bounded by a plasma membrane similar to that around 
any vacuole in the cell. Lawson (:03) and Grégoire and 
Wygaerts (:03) have emphasized this structural condition in 
recent papers but the central idea seems to be an old one run- 
ning through the writings of Strasburger from an early period. 
We bring up these striking conceptions of nuclear structure 
in the higher plants because it seems very probable that a much 
clearer understanding of the problems will come through inves- 
tigations upon the simpler conditions in the lower plants. 
There, we may hope to find evidence of the primitive forms of 
nucleolar and chromatic associations with perhaps some clues as 
to the manner of the development of the higher types of struc- 
ture. Thus the yeast cell, as reported by Wager ('98) with its 
chromatin sometimes collected within a vacuole and sometimes 
distributed in the cytoplasm and a nuclear body (nucleolus) in 
close association with the nuclear vacuole, but not within, is of 
the greatest interest as presenting intermediate stages in the 
complexity of nuclear structure and illustrates what may be 
hoped from further research among the lower forms. 
The Chromatophore and Plastid.— In considering the great 
‘variety of chromatophores and plastids exhibited among the 
