86 W. G. RIDEWOOD AND H. B. FANTHAM. 



host tissue. The capsule and this latter layer are refringent, 

 and yellowish-brown in colour ; they seem to be chitiuous, 

 but special tests were not applied. 



These chitinoid layers are not always present, and eveu 

 when they are to be recognised, they are so indefinite and 

 irregular that we prefer not to use the word cyst at all, but 

 to employ a more indefinite term, such as capsule. Probably 

 the layers in question are produced by the host tissue in an 

 attempt, unsuccessful as it appears, to isolate the parasite 

 from orgauic connection with itself, or else they consist of 

 broken-down nerve tissue which has taken a more or less 

 spherical shape in accommodating itself to the space between 

 the parasite and the still healthy part of the host tissue. 



In some of the cavities a coagulum is to be noticed sur- 

 rounding the parasite (fig. 7, coag., also figs. 5 and 6). The 

 coagulum is probably directly connected in its origin with the 

 degeneration of the host cells, and the production of the 

 capsule. 



Structuke and Life-cycle op Neurosporidium. 



The pai'asites in their smallest phase occur as little round 

 or oval cells (free spores or amgebulas), about 3^ (2 to 4^) in 

 diameter (see fig. 3), each with a single nucleus. These are 

 found lying in or among the nerve cells of the host, having 

 apparently entered this tissue by infiltration. It is not 

 possible, with the material at our disposal, to say definitely 

 if there is an intracellular phase of the parasite within a 

 nervous epithelial cell at the beginning of the life-history of 

 the parasite. Nuclear division takes place in the amEebula, 

 and young trophozoites, with two or three nuclei in a some- 

 what iri-egular mass of protoplasm (fig. 3, h, c, d) are of 

 common occurrence, often lying in a space among the 

 nervous tissue cells of the host. Figures of nuclear division 

 (fig. 3, c) are very rarely and imperfectly seen in our material. 



The young trophozoites are usually about 5 ju in diameter. 

 The protoplasm of the trophozoite at this stage is granular 



