254 Rickett.—Fertilization of Sphaerocarpos. 
may express themselves, in different plants, by influencing in different ways 
the structure of the cytoplasm ; the difference may also be exaggerated by 
differences in technique. 
The concentration of certain materials in the cytoplasm about the egg 
nucleus may be a phenomenon of general occurrence. Mention has already 
been made, under Phase i, of the variety of forms in which this has been 
partially described or figured. It is interesting also to note that Gayet ( 1897 ) 
describes the egg of Sphagnum as containing in its cytoplasm numerous 
rounded bodies, which he calls chromatophores. The cytoplasm of the 
fertilized egg of Preissia quadrat a , as described by Miss Graham ( 1918) 5 is 
in a similar condition, and the rounded bodies are more numerous around 
the nucleus. It is possible that the rounded bodies described by these 
authors bear the same relation to the denser portions of the cytoplasm 
noted by others as do the granules of the egg of Sphaerocarpos to the more 
usual homogeneous mass that surrounds the nucleus. 
Fertilization in the Bryophyta. 
The various cases, mentioned in the introduction to this paper, of 
fertilization in Liverworts observed and figured by previous writers harmonize 
very easily with the complete history as here presented for Sphaerocarpos. 
Although in most of the cases previously described only one stage, or 
several stages almost alike, were seen, and although various interpretations 
were placed upon these few stages, it seems possible that fertilization may 
follow the same course in many Liverworts as it does in Sphaerocarpos. At 
all events, in all cases (except two) so far described, the male nucleus enters 
into a resting condition before fusion with the female nucleus; and whether 
an actual fusion occurs, and in what condition the nuclei fuse, is not known 
with certainty in any Liverwort, not excluding Sphaerocarpos. Of the two 
exceptions mentioned, one is the case of Riella described by Kruch ( 1891 ), 
in which the male nucleus seems to proceed to the organization of chromo¬ 
somes immediately after its entrance into the egg and while it is taking on 
a spherical form. More modern methods might perhaps throw more light 
on what actually takes place here. The other divergent case is found in 
Fossombronia , as reported by Humphrey ( 1906 ). Here the antherozoid, or 
at least its nucleus, retains its vermiform shape after entering the egg cyto¬ 
plasm. Its subsequent behaviour was not observed. Some unpublished 
and as yet incomplete results of Mr. A. M. Showalter (to whom I am 
indebted for allowing me to see his figures) show what is apparently the 
same condition in Riccardiapinguis , and also seem to indicate that the still 
vermiform or coiled antherozoid penetrates the female nucleus, much as is 
the case in some ferns (Shaw, 1898 ; Yamanouchi, 1908 ). These two last- 
cited cases among the Jungermanniales suggest that the behaviour of the 
nuclei in fertilization may be quite different for the Jungermanniales and 
