Wilson. — Spermatogenesis in the Bryophyta. 417 
the middle part loosens and forms the vesicle. In the Musci 1 a spermato- 
zoid develops in each cell of the inner tissue of the antheridium. 
Buchtien ( 15 ) in 1887 gave a short account of the development of the 
spermatozoid in Petlia epiphylla. The body is formed directly from the 
nucleus of the mother-cell, while the cilia are outgrowths of the cell plasma. 
The discoid spermatids are figured in pairs, and a wall is shown separating 
the two, while at a later stage each developing spermatozoid is represented 
completely surrounded by a wall. 
The formation of two spermatozoids from each mother-cell of Pellia 
epiphylla was also described by Campbell ( 16 ) a few years later, but no wall 
is shown between the two spermatids resulting from the division. In the 
Musci Campbell emphasizes the presence of a highly refractive mass found 
at the posterior end of the spermatozoid ; this, in Sphagnum acutifolium , 
still contains starch at the end of development. 
Leclerc du Sablon ( 39 ) in 1888 gave a description of the formation 
of spermatozoids in several of the Hepaticeae. In Metzger ia furcata the 
nucleus passes to the surface of the mother-cell, still retaining its usual 
form. Meanwhile, a protoplasmic band differentiates around the cell, touch- 
ing the nucleus at one point. This band gradually thickens and becomes 
intimately fused with the nucleus, which decreases in size, owing to the trans- 
ference of its material to the band. Finally, the nucleus completely dis- 
appears, while the band opens out and by growth in length forms the body 
of the spermatozoid. The cilia appear when the body is completely formed. 
The development in Radula , Frullania , and Alicularia is similar. 
Guignard (26 a) in 1889 gave a careful account of development of the 
spermatozoid in the Characeae, Bryophyta, and Pteridophyta, and in all these 
groups he emphasizes the fact that the principal part of the spermatozoid is 
derived from the nucleus. In Pellia epiphylla he found that the mother- 
cells of the spermatozoids are placed in pairs and are discoid, and he figures 
them separated by a distinct wall. The spermatozoid is produced by the 
growth in length of the nucleus, the cilia arising from a mass of hyaline 
protoplasm at the anterior end. The development in Anthoceros laevis 
is similar, but here the mother-cells are described as being originally rect- 
angular, becoming biconvex at a later stage. Other genera of the Hepaticae 
were examined, and these, together with the Mosses, agree in general with 
the above account. In Sphagnum fimbriatum each spermatid is shown sur- 
rounded by a wall ; during the development an amylaceous mass of proto- 
plasm is found at the posterior end of the nucleus, and this persists un- 
diminished in amount in the vesicle. At the anterior end of the body 
a small highly refringent ‘ bouton ’ is present which carries the cilia. 
The account given by Schottlander ( 58 ) in 1892 differs from those 
of other investigators in the discovery of two distinct portions in the body 
1 p. 37 6 * 
