Notes on the Genus Toxoplasma. 



293 



breaks up. The parasites are sometimes found in the nucleus itself ; of this 

 an example is shown in Plate 9, fig. 2. There is a tendency for these 

 leucocytes to mass themselves together, but no true giant-cells are formed. 

 Very few parasites were found in the endothelial cells of these three animals ; 

 a few were found in the omentum of the fossa and in the mesentery of the 

 fruit pigeon. This is quite contrary to the experience of Miss H. L. M. 

 Pixell (5), who found cells containing large numbers of the parasites from 

 these situations. 



The multiplication of the Toxoplasmas is effected ordinarily by longitudinal 

 division. The nucleus first enlarges, then becomes rod-shaped, and later 

 of dumb-bell shape, and eventually the daughter nuclei are formed, the cell 

 having already begun to divide. I have seen no example of transverse- 

 division in these cases. In the bone-marrow of the fossa several round 

 cysts were found in enlarged leucocytes, which suggested schizogony (Plate 9, 

 fig. 3), and these are somewhat like the schizont in the Coccidia when it is 

 about to divide up into merozoits ; and in the Say's snake (Plate 10, fig. 9) 

 there is a structure which is apparently a later stage, showing the formation 

 of merozoits. No flagellated forms have been seen. 



Many attempts at cultivation in various media were made, but none were 

 successful. 



The Toxoplasma has a very wide geographical as well as zoological 

 distribution. The three cases here recorded came respectively from 

 Madagascar, the Aru Islands, and Mexico, and those previously described 

 by various observers were found in Brazil, Tunis, Italy, Japan, and Germany. 



The varieties to be described were found in the course of the post-mortem 

 examination of the animals which have died in the Zoological Gardens, and 

 the following paragraphs will indicate the distribution of the parasites and 

 the points of difference between them :— 



I. Fossa, Cryptoprocta ferox, from Madagascar. Plate 9, figs. 1-3. 



The animal was very wasted. Both pleural, peritoneal, and pericardial 

 cavities contained a quantity of blood-stained fluid. The lungs and kidneys 

 were very congested, and there was a layer of lymph on the under-surface 

 of the diaphragm. The blood was extremely anaemic, and contained many 

 poikilocytes and nucleated erythrocytes. A few Toxoplasmas were found in 

 the blood ; many were found in the blood from the lung, and in the pleural 

 and peritoneal exudation, and in the bone-marrow. Few were found free ; 

 nearly all were contained in the large mononuclear leucocytes, often a great 

 number, as many as 36, in a single leucocyte. The leucocytes were very 

 much enlarged, and their protoplasm was extremely thin and delicate, many 



2 b 2 



