. 
312 The American Naturalist. [April, 
nucleus of the cancer cell when it bursts through over-disten- 
sion with parasites, perishes, but when only one or two para- 
sites escape, it usually heals up perfectly. 
For the further life history of protozoa of cancer, we may 
follow Mr. Jackson Clarke.’ In describing his examination of 
a myeloid sarcoma, he says: “In the most interesting portion 
of the neoplasm, its advancing border, the entire peripheral 
zone of the section could be examined from end to end with- 
out anything but ameeboid psorosperms and remains of infil- 
trated connective tissues coming into view. In the centre of 
the field [Fig. 5] is a psorosperm in the plasmodium stage, in 
which spore-formation is commencing. Below is part of a 
giant cell containing one encapsuled and two ameeboid psoro- 
sperms ; numerous free amceboid parasites, and to the left is 
part of a large plasmodium, within which are nuclei and 
fibres undergoing digestion. 
In this sarcoma, as in all the cancers, I have examined Te- 
cently, there is, in the advancing zone, an army of ameeboid 
psorosperms invading and digesting the tissues beyond, and 
determining new growth in the special tissue with which the parasites 
have established a symbiosis. For it appears that the curious 
inter-dependence of two organisms, known as symbiosis, has 
*Sarcoma Caused by Psorosperms. By J. Jackson Clarke, M. B., FROS 4 
Medical Journal, Dec. 24, 1892, and Jan. 21, 1893. 
