536 
Woodburn. — Spermatogenesis in 
in operation, and the regular appearance of fundamentally significant 
structures which indicate natural relationships. The visible architecture of 
the cell is constantly changing. A nuclear or cytoplasmic structure of a 
certain pattern may be organized, pass through a series of changes, and 
then apparently be resolved again into less highly differentiated protoplasm. 
While throughout the majority of the plant groups we recognize the constant 
separation of the protoplast into nucleus and cytoplasm, the majority of 
certain forms (for example, the Schizophyta) fail to exhibit this differentiation. 
There is also a time in the life-history of a Bryophyte when an intimate 
union, if not an intermingling, of nucleus and cytoplasm seems to exist.* 
The protoplast which forms the male gamete exhibits at early stages the 
usual sharp division into nucleus and cytoplasm. As the sperm reaches 
maturity, this sharp distinction between nucleus and cytoplasm becomes 
less defined. Perhaps in no other case is the morphological unity of the 
protoplast as a whole more clearly demonstrated. Within this unit there is 
a distinct organization of the elements, which are constantly mobile, and 
which become grouped according to definite laws, with the consequent 
appearance of visible protoplasmic structures. The individual protoplast as 
a unit of organization is clearly apparent. The writer does not wish to 
minimize the value of minute structural details, but merely to emphasize at 
the same time the power of the protoplast to develop along definite mor- | 
phological and physiological lines with considerable plasticity of structure. 
The following data from Asterella confirm largely the writer’s previous 
conclusions in regard to other Bryophytes. 
The Prophase in Antheridial Tissue. 
The fixed and stained cytoplasm of an antheridial cell in a resting con- 
dition contains very finely divided granules (PI. XX, Figs, i and 2). These 
granules are not evenly distributed, but are aggregated irregularly into 
flocculent masses. These masses are of varying density and structure. One 
may find more or less uniform gradation from open, granular cytoplasm, 
through areas of more closely grouped granules, to larger, deeply-stained 
lumps. That these larger granules appear in any definite number or pattern, 
the writer finds no evidence. 
The nucleus contains an irregular network of relatively large granules 
with one larger, centrally-placed, spherical body which resembles a nucleolus 
(Figs. 1 and 2). A faintly-stained or quite clear region may completely 
surround this central body. In or around this body, or nucleolus, the 
chromatin gradually collects 'during the prophases of division (Figs. 1, 2, 
and 3). As a result, this central mass gradually loses its regularly spherical 
form and becomes a larger group of irregular chromatin lumps, which 
presents somewhat the appearance of synapsis in spore-mother-cells (Fig. 4). 
Occasionally (Fig. 4) one lump stains like a nucleolus as compared with the 
