Osborn.— Spongospor a subterranea , ( Wallroth ) Johnson. 335 
may possess more than one nucleolus, and have densely granular nucleo- 
plasm. By the time of the first karyokinesis, the host cell nucleus would 
appear to have degenerated or to have been absorbed by the parasite ; it 
is not generally to be observed later than the akaryote stage. No multi- 
nucleate host cells have been observed, nor do the host cells appear to be 
much enlarged, which is an interesting point of difference from the cells 
attacked by Sorosphaera Vero?iicae and Plasmodiophora , though in S. Junci 
their behaviour is similar. 
In the last few years a number of papers have appeared adding to 
our knowledge of the Plasmodiophoraceae and the allied groups. These 
have been summarized recently in the ‘ Progressus Rei Botanicae V but it is 
necessary to review some of the salient points here. 
Nawaschin’s 2 account of Plasmodiophora in 1899 described a method 
by which the amoebae infected new host cells, which is similar to that 
given here. The nuclei of the amoebae were found to divide in a special 
manner, differing markedly from indirect nuclear division. The ring of 
chromatin matter around the karyosome is described, also something in the 
nature of an achromatic spindle, but neither centrosomes nor polar radiations 
are mentioned. Spore formation was found to be preceded by plasmodium 
formation, followed by a reconstitution of the nuclei and their subsequent 
karyokinetic division. 
In 1905 Prowazek’s 3 description gave still further details of the divisions 
in the vegetative phase. Centrosomes and asters were described, and a dis- 
tinction drawn between the tropho- and idiochromatin stated to be present 
in the divisions. The chromidial stage was described in great detail, also 
the presence of two karyokinetic divisions subsequent to it, which are referred 
to as generative divisions. Following these divisions the protoplasm is stated 
to round itself off about the nuclei. These uninucleate bodies unite in pairs 
before encystment. The spore membrane then forms, and the nuclei within 
the cyst divide ; one nucleus from each pair then degenerates, while the 
remaining two nuclei fuse. Prowazek regards this division in the cyst as 
the reduction division, the two karyokineses in the plasmodium having no 
such significance. 
Maire and Tison, 4 in their memoir on the group, state that they are 
unable to agree with Nawaschin that a plasmodium formation occurs, since 
they have several times observed in the same cell an amoeba in the metaphase 
and another in the anaphase of the sporogenous division. They agree with 
Prowazek on the matter of a double karyokinesis, but are quite unable to 
accept his statement as to the autogamy succeeding encystment, which they 
consider simply as an abnormal occurrence. 
In addition to Plasmodiophora , Maire and Tison have in the same 
1 Pavillard, J. : Prog. Rei Bot., vol. iii, 1910, p. 474. 2 Nawaschin, S. : loc. cit., 1899. 
3 Prowazek, S. : loc. cit., 1905. 4 Maire, R, and Tison, A. : loc. cit., 1909, p. 239. 
