Wilson. — Spermatogenesis in the Bryophyta. 419 
morpha. In this plant the rectangular cells of the developing antheridium 
possess vacuolated protoplasm and a nucleus bounded by a distinct mem- 
brane. During the early stages of division a small body appears in the 
nucleus and soon moves towards the membrane, producing a beak-like 
swelling in it. This body passes into the cytoplasm, becomes constricted, 
and then divides, giving rise to two structures which pass to the opposite 
sides of the nucleus ; these are the centrosomes. Although no cytoplasmic 
radiations are present these can be clearly distinguished, as no other granules 
are present in the cytoplasm. The nucleus now elongates towards the 
centrosomes, and spindle fibres stream out from the latter ; eight chromo- 
somes are found on the equatorial plate. During the later stages the 
centrosomes are only occasionally seen, and they finally disappear, being 
probably taken up in the daughter nuclei. All the divisions in the develop- 
ing antheridium are similar, the centrosomes arising afresh during each 
prophase, but the last division is characterized by the diagonal position 
of the spindle and by the persistence of the centrosomes in the resulting 
daughter-cells. The latter are at first triangular in section, and no wall 
is present between them. Up to this time the majority of investigators had 
regarded the rectangular cells in the antheridia of the Hepaticae as the 
spermatozoid mother-cells. This was the view taken by Strasburger (65) in 
the ‘ Botanisches Praktikum ’ in 1902, although Thuret (68), as early as 1851, 
had described the discoid mother-cells in several species, and Goebel (25) in 
Pellia epiphylla had pointed out that each rectangular cell produced two 
spermatozoids. The triangular cells soon become rounded, and the centro- 
some which now functions as a blepharoplast moves towards the end of the 
cell, becomes elongated, and develops the two cilia. Meanwhile, a fairly 
large spherical body which takes up the chromatin stain has appeared 
in the cell ; the origin of this ‘ chromatoider Nebenkorper ’ was not deter- 
mined, and at a later stage it disappears, taking no part in the formation 
of the spermatozoid. A cytoplasmic band now becomes differentiated 
which connects the blepharoplast and the nucleus, and the latter, which has 
become homogeneous in structure, elongates, and together with the cyto- 
plasmic process forms the body of the spermatozoid. 
Ikeno considered that the production of two spermatids from a mother- 
cell is a general rule for all Bryophytes, both Mosses and Liverworts. He also 
concluded that typical centrosomes are present in all cell generations in the 
antheridia of the Bryophyta, and that after the last division they change 
their function and act as blepharoplasts. 
In a later communication Ikeno (33), as a result of further investigation, 
modified the above conclusions. He found that in A trichum angustatum 
and Pogo 7 iatum rhopalophorum no centrosomes are present during the cell- 
divisions in the young antheridium ; in both these Mosses eight chromo- 
somes appear during mitosis. In Makinoa crispata also no chromosomes 
