762 SAECOSPORIDIA 



end is an elongate nucleus consisting of a membrane and central karyosome. 

 The cytoplasm of the spore towards the pointed end is clear and hyaline, 

 while the rest contains a number of granules of a material which stains 

 deeply. The clear portion was supposed to be of the nature of a polar 

 capsule, chiefly as a result of the statements of Van Eecke (1892), who 

 claimed to have produced an extrusion of filaments as occurs in the spores 

 of Microsporidiida. This observation has never been confirmed, and it 

 seems evident that the clear part of the spore contains nothing but hyaline 

 cytoplasm, and in no way corresponds with the polar capsules of the 

 Microsporidiida, A fully-grown parasite will contain many thousands of 

 spores, which escape when rupture takes place. 





Fig. 327. — Diagrammatic Representation of Longitudinal Section of a 

 Sarcocyst in the Muscles of the Ox (xea. 500). (Original.) 



Life-History. — The development of the parasite has been studied 

 chiefly in experimentally infected mice. Erdmann (1910, 1910a, 1914) 

 states that in the intestine of the mouse the spore membrane ruptures and 

 liberates a small amoeboid body which enters the intestinal cells. There 

 follows a period of multiplication. The parasites persist in the gut wall 

 for a few days only. They then disappear, and are only detected about 

 forty days later in the muscle fibres. According to Negri (1910), who 

 studied experimental infections in rats, the youngest forms seen in muscle 

 fibres have a length of 25 microns, and are cytoplasmic bodies contain- 

 ing about twelve nuclei (Fig. 328). Segmentation of this multinucleate 

 Plasmodium then occurs, so that a number of cells are enclosed in a mem- 

 branous sheath. This development occupies from forty-eight to sixty 

 days. The sheath may rupture, and the cells wliicli are liberated infect 



