280 DR. LILY BATTEN ON 
by a protoplasmic strand. The tetrasporangium divides into two transversely, 
the basal cell remaining inconspicuous, while the upper one grows rapidly. 
The wall becomes definite and the contents assume a dark colour. The nucleus 
of the tetraspore mother-cell has been shown by Yamanouchi (62. p. 401 
et seq.) to contain 40 chromosomes, and as a result of reduction division the 
nuclei of the tetraspores contain only 20. After the division of the nucleus, 
the contents of the mother-cell divide into four parts, which arrange 
themselves in a definite way. One remains at the base of the cell near 
the point of communication with the basal cell, two occur over this one, and 
the fourth at the top of the large oval cell. As the tetraspores increase in 
size, the neighbouring siphons become pushed outwards, resulting in a 
distorted ramulus. 
Antheridia. 
The antheridia are developed at the tips of the branches, where they either 
replace the whole of one of the jointed filamentous hairs, or else one arm of 
the first branch of a dichotomous hair. In material of P. nigrescens from 
Plymouth Sound each antheridium replaced an entire hair, and the fila- 
mentous axis was continued for a considerable distance beyond the tip of 
the antheridium. he antheridia are elongated, somewhat cylindrical, and 
often slightly curved. The structure of the antheridium has been described 
by Yamanouchi (62. p. 401 et seg.). A filamentous axis extends down the 
centre, and on this the flattened stalk cells are borne. The sperm mother-cells 
which give rise to the antherozoids are formed on the stalk cells, and large 
numbers of oval sperms are developed, each containing a large vacuole. 
> 
Cystocarps. 
The development of the cystocarp has been worked out in detail by Phillips 
(46 & 47. pp. 289-301), Schmitz (50), Yamanouchi (62. p. 401 et seq.), and 
others. Oltmanns (44. p. 99 et seg.) showed that the real sexual act is the 
union of the male and female gamete nuclei in the carpogonium, and that 
the auxiliary cells are probably only concerned with the nourishment of the 
cystocarp. Previous to this work, the act of fertilization and the secondary 
fusions concerned with the auxiliary cells were all included in the sexual 
process. 
According to recent work by Yamanouchi (loc. cit.) and Phillips (loc. cit.) 
the procarp in P. violacea consists in the beginning of a short branch of three 
or four cells. The most important of these is the cell of the axial siphon 
lying next to the apical cell. This divides to form five pericentral cells, which 
completely surround it. Que of these is the “ pericentral cell," which will 
give rise to the carpogonial branch. The nucleus of the pericentral cell 
divides nearly parallel to the axis of the procarp, cutting off a cell which 
develops the carpogonial branch. The pericentral cell later gives rise to a 
group of auxiliary cells. The carpogonial branch consists of four cells, the 
terminal of which becomes the carpogonium and develops a trichogyne. 
