42 Blomfield and Schwartz.—Observations on the Tumours on 
only a few atrophied and degenerate nuclei are to be seen in the infected 
cells. Thus it is here, as in other cases of plant and animal parasitism, that 
the activities of the cell are moulded to suit the requirements of the 
parasite. The action of the parasite on the cell in the early stages does 
not seem to be injurious, and one might imagine that if the parasite could 
be extracted from the cell in an early stage, the latter would resume its 
normal mode of life and fulfil its destiny as a cambial cell. 
Comparison with Plasmodiophora. The life-history of our parasite 
shows great similarity to that of Plasmodiophora , to which it is evidently 
nearly related ; the various stages in the nuclear division, as described by 
Nawaschin and Prowazek in their papers, are identical with those we have 
observed in Sorosphaera ; this similarity, however, ends in the terminal 
phase, in which we get the spores enclosed in a membrane ; this would 
perhaps correspond to the capillitium of non-parasitic Mycetozoa. The 
nuclei of Sorosphaera are somewhat larger than those of Plasmodiophora , 
and the vegetative stage of the former is more commonly met with than 
that of the latter, in which the reproductive stage is the more common. 
We have not, however, been able to agree in all particulars with the 
account of P. Brassicae as given by Nawaschin and Prowazek, though in 
the main the life-histories of both parasites are similar. Thus we have 
failed to find any evidence of conjugation of the amoebulae, though, as we 
have stated, they may be seen in close proximity, but we see no reason to 
consider this as the commencement of a conjugation rather than the result 
of a division. We fail also to observe any extrusion of polar bodies. 
In the article on Mycetozoa in Lankester’s Treatise on Zoology there 
is a sub-class Sorophora, embracing those forms which have no true plas- 
modium ; Sorosphaera , we think, might be assigned to this ; Plasmodiophora , 
however, is classed among the Proteomyxa. 
In Arthur Lister’s work on the Mycetozoa there are figures which 
suggest that there are two forms of nuclear division, a vegetative and 
a reproductive ; further investigation on the nuclear division of non-parasitic 
Mycetozoa may throw light on their relationship to the parasitic ones. 
Summary and Conclusions. 
1. The tumours found on the stems and leaves of Veronica Chamae- 
drys are caused by the invasion of a Mycetozoan parasite, Sorosphaera 
Veronicae. 
2. The life-history of Sorosphaera may be divided into three stages, 
viz. the Vegetative, the Akaryote or Chromidial, and the Reproductive, 
each being characterized by a difference in the nuclei. 
3 The parasite has no power to penetrate through the cell walls, 
