228 Rickett.—Fertilization in Sphaerocarpos. 
Both nuclei are in the resting condition. In the cytoplasm of the egg lies 
an elongated plastid. 
In the Mosses the state of our knowledge of fertilization is even more 
unsatisfactory. 
The entrance of the antherozoids into the archegonium was seen 
by Roze (1872) in Sphagnum cymbifolium, and by Arnell (1875) in Disce- 
lium nudum. The former figures many antherozoids clustered about the 
opening of the neck, several passing down the neck, and one in the venter 
just touching the egg. They enter the neck with the ciliated end ahead, 
and retain the cytoplasmic globule at the posterior end, carrying it with 
them into the venter. Arnell described the entrance into the venter of 
many antherozoids which impart to the egg a rocking movement. After 
this ceases, the surface of the egg is papillose, owing to the incompletely 
absorbed antherozoids. He was unable to distinguish the antherozoids 
after they had penetrated the egg. 
Gayet (1897) also saw the entrance of many antherozoids into the 
archegonium of Fissidcns mcurvus , but discerned no rocking movement 
of the egg. Only one antherozoid penetrates the egg. This becomes first 
crescent-shaped, then spherical, and finally fuses with the egg nucleus, 
while the thin envelope of cytoplasm with which it has been surrounded 
fuses with the cytoplasm Of the egg. The female nucleus possesses at this 
time four very distinct chromosomes, which seem drawn towards the male 
nucleus. Gayet followed the same history in Bryum capillare up to the 
crescent-shaped stage of the male nucleus. He also described abnormalities 
in the archegoniaof various Liverworts, such as supernumerary ventral canal 
cells, and reported the fertilization of the ventral canal cell instead of the 
egg in Marchantia . 
The Leeuwen-Reijnvaans (1908 a) described a remarkable series of 
events in the fertilization of Polytrichum . According to their account, 
reduction divisions occur in both antheridium and archegonium. The egg 
and the ventral canal cell then fuse, and the cell resulting from this fusion is 
feitilized by two antherozoids, this double fusion restoring the sporophytic 
number of chromosomes. The antherozoids maintain a slender form in the 
cytoplasm of the cell formed by the fusion of the egg and the ventral canal 
cell, but take on the appearance of resting nuclei when they come in con¬ 
tact with the female nucleus. The membranes of the three nuclei then 
disappear. In a subsequent paper the same authors (1908 £) described 
a similar £ double reduction ’ in Mnium . The spermatogenesis of Poly¬ 
trichum has been investigated by Walker (1913), and that of Mnium by 
Wilson (1911). Both of these authors reported nuclear divisions of the 
usual type, without reduction. Walker also found that the egg and ventral 
canal cell of Polytrichum do not regularly fuse, and attributes the results of 
the Leeuwen-Reijnvaans to their technical methods. 
