48 SPERMATOGENESIS AND FECUNDATION OF ZAMIA. 
wall into which the short ends of the spindle fibers extend, and in 
which their gradual transformation into the ordinary reticular struc- 
ture of the protoplasm seems to be taking place (fig. 44). Ordinarily 
the double plasma membrane can not be distinguished readily, but in 
some instances it is plainly discernible, being due evidently to slight 
contraction. In the case of the division of the central cell which gives 
rise to the spermatids no cellulose well is formed between the cells. 
In cases where such a wall is formed or normally occurs it would 
doubtless be laid down between the two plasma membranes. As to 
the question of the division of the swellings on the spindle fiber into 
two portions in the formation of a double plasma membrane no eyi- 
dence has been obtained. The two membranes normally appear as a 
single membrane and apparently, unless there is some contraction, the 
presence of a double membrane can not be determined. The details 
of the origin of the plasma membrane here correspond in general, so 
far as traced out, with the conclusions of Strasburger. A double 
plasma membrane, such as is seen in the central cell of Zama, is also 
described by Blackman (16, p. 400) in the formation of the ventral 
canal cell in Penus. | 
In a stage slightly later than the one above described the division 
may be considered as completed; the daughter nuclei having appar- 
ently returned to the resting condition (fig. 36). The organization of 
the cilia-bearing band, however, is yet incomplete. The band and 
blepharoplast granules still lie free in the cytoplasm, about midway 
between the nucleus and the plasma membrane. The band by this 
time has grown to an appreciable thickness and increased greatly in 
length. It now forms a crescent-shaped body with the granules 
grouped on one side (figs. 38 and 64). The band in this stage is 
usually about 7 to 10 “# in width at broadest point. : 
METAMORPHOSIS OF THE SPERMATIDS. 
‘ After careful consideration the writer has concluded to adopt the 
zoological term spermatids in designating those cells which become 
metamorphosed directly into spermatozoids. The change in the 
daughter cells from the closing of the division of the central cell up to 
the maturing of the spermatozoids is thus discussed under the heading 
Metamorphosis of the Spermatids. The nomenclature here used 
corresponds with that used by Shaw (102) in JJarsilia. The use of 
spermatid and spermatozoid instead of antheroblast and antherozoid, as 
the writer at first intended, seems commendable as terms having a 
corresponding meaning in zoology and thus more generally under- 
stood. ‘The central cell and intermediate cell generations can not be 
given terms similar to the zoological ones, as the process of devel- 
opment in plants is very different from that of animals, the reducing 
