Notes. 
2 35 
PRELIMINARY NOTE ON THE SPERMATOGENESIS OF MNIUM 
HORNUM.—In a recent paper Arens 1 has investigated the spermatogenesis of 
Polytrichum juniperinum and Mnium hornum and finds that in both cases the nuclear 
divisions are of the normal type. In the latter plant eight (later corrected to six 1 2 3 ) 
chromosomes of equal size appear at each mitosis. Drs. van Leeuwen-Reijnvaan 3 4 
have also described the spermatogenesis in several Mosses, and in all the 
plants examined they state that a reduction in the number of chromosomes takes 
place at the final division of the spermatogenetic cells. In Mnium sp. 4 eight chromo¬ 
somes are present, four being long and four short, and, at the last division, two long 
and two short chromosomes pass to each daughter-cell. 
In the present investigation no such reduction has been discovered. The early 
divisions in the antheridium resemble the premeiotic mitoses already described in the 
developing archesporium, 5 with the difference that here six chromosomes are present. 
During the early stages of the penultimate and of the final division a body is cut off 
by constriction from the nucleolus, similar to that described in the first meiotic 
division ; 5 this body has not been observed to pass outside the nuclear membrane as 
long as the latter is present. No centrosomes are found during the later stages 
in these or in the earlier division figures. The resting nucleus, before the final 
division, is of large size in relation to the cell, but possesses a small nucleolus. A con¬ 
tinuous spireme is not present, the chromatic material first appearing in a number of 
small masses, and from these the chromosomes are gradually formed. Stages show¬ 
ing the six free chromosomes are frequently found ; the latter are usually curved 
and intertwined, but are of approximately equal size. The metaphase is normal and 
is quickly passed over, the axis of the spindle usually coinciding with the long axis of 
the cell; there is no diagonal division. In polar views of the anaphase six chromosomes 
can be distinguished, and it is quite clear that no reduction has taken place. The telo¬ 
phase is normal, and is characterized by the presence of large vacuoles in the 
cytoplasm. The spermatocytes each possess a distinct wall, but the protoplasm soon 
contracts away from this, forming a rounded mass ; a large vacuole is usually present. 
The nucleus is large and contains a small deeply staining nucleolus. 
The development of the spermatozoid from the spermatocyte is a very complex 
process, and full details of this and of the preceding divisions will be given in 
a further communication. 
M. WILSON. 
Royal College of Science, 
S. Kensington. 
Dec. 1909. 
1 Zur Spermatogenese der Laubmoose. Inaugural-Dissertation, Bonn, 1907. 
2 Zur Spermatogenese der Laubmoose. Ref., Bot. Centralblatt, Bd. cvii, 1908, p. 611. 
3 Uber eine zweifache Reduktion . . . bei einigen Polytrichum- Arten. Recueil des Travaux 
botaniques N^erlandais, iv, 1907. 
4 liber die Spermatogenese der Moose. Ber. d. deutsch. Bot. Gesell., Bd. xxvi a, 1908, p. 301. 
5 Wilson, M.: Spore Formation and Nuclear Division in Mnium hornum. Annals of Botany, 
xxiii, 1909, p. 141. 
