449 
Mnium affine , var. ciliaris (Grev), C.M. 
geneously staining substance. Vacuoles and dark staining lumps may 
appear in the cytoplasm (Figs. 13, 14, 16, 20, 22, and 23). The part 
apparently representing the nucleus may also appear vacuolate. A very 
close association seems to exist between nucleus and cytoplasm on the 
one hand, and nucleus and blepharoplast on the other. Probably there 
is a free interchange of materials at certain stages between these three 
structures. There does not seem to be the appearance, with sufficient 
constancy, of structures other than the nucleus, the cytoplasm, and the 
blepharoplast with the cilia, to warrant a separate designation of other 
bodies such as limosphere or accessory body. Furthermore, as develop¬ 
ment proceeds there is the tendency for the sharp distinction between 
nucleus, cytoplasm, and blepharoplast to disappear. 
Vacuoles in the Cytoplasm of the Sperm-cell. 
The structure described by Wilson as a limosphere is a spherical body 
which may contain substance staining like cytoplasm, or may be hollow in 
the nature of a vacuole. Certain of Wilson’s figures of the ‘ limosphere ’ 
correspond quite closely to my Figs. 14, 16, 23, and 28. Black also 
reports a vacuole in the cytoplasm of Riccia Frostii. Figs. 22 and 23 
represent nearly the same stage of development, but do not represent 
similar conditions of vacuolate cytoplasm. The cytoplasm in Fig. 22 
contains a number of vacuoles, while that in Fig. 23 contains only one. 
Such a vacuole as is shown in Fig. 23 gradually disappears (Figs. 28 and 
29). The relation as regards position which this vacuole bears to the main 
body of the sperm suggests that the latter may receive the finely granular 
substance which bounds the former. The small granule shown in Fig. 14 is 
not in the centre, but lies at least near and probably upon the surface of the 
vacuole. The granule in Fig. 15 may represent the same kind of body. 
Possibly these are nucleoli which have become free in the cytoplasm. 
Nucleoli, or fragments of nucleoli, are doubtless frequently left free in the 
cytoplasm of higher plants during karyokinesis, when the nuclear membrane 
does not longer separate chromatin and cytoplasm. There is, at least, con¬ 
siderable evidence to support the theory that during this transformation of 
the sperm-cell, the nuclear membrane may to a certain extent break down 
(Figs. 13, 14, and 16), and that an exchange of substances between nucleus 
and cytoplasm may take place. 
A slightly different condition is represented in Figs. 21, 25, 26, and 27, 
where we do not find the spherical vacuole, but a region or group of 
vacuoles. The granular substance connected with these, instead of forming 
a hollow sphere, produces a distinct network or mesh, which reminds one 
very much of the vesicle that has been described for the sperm of more or 
less closely-related forms. That this vesicle also gradually disappears 
is clearly evident from a comparison of Figs. 21, 25, 26, and 27. The fate 
