432 PROCEEDINGS OF THE ACADEMY OF [May, 



THE EVOLUTION OF SARCOCYSTIS MURIS IN THE INTESTINAL CELLS OF 



THE MOUSE. 



(Preliminary Note.) 

 BY HOWARD CRAWLEY. 



As long ago as 1903, Minchin (1903, p. 308), speaking of the 

 Sarcosporidia, observes that "there is still much to be made out about 

 these interesting parasites, and the field is one ripe for investigation." 



Since that time it cannot be said that our knowledge of the group 

 has been materially increased. A number of papers on the Sarco- 

 .sporidia have indeed been published, but these have been concerned 

 with the character of the spores and cysts rather than with any 

 attempts to elucidate the life history of this group of the Protozoa. 

 The exception is a contribution by Erdmann (1910, p. 377), the 

 results of which are summed up and commented upon by Minchin 

 (1912, pp. 421, 422) as follows: 



"According to Erdmann, the spore germinates in the intestine of 

 the new host, and the first act in the process is the liberation from 

 the spore of its toxin, sarcocystine, which causes the adjacent epithe- 

 lium of the intestine to be thrown off. At the same time an amoebula 

 is set free from the spore; and, owing to the intestine being denuded 

 of its lining epithelium, the amoebula is able to penetrate into the 

 lymph-spaces of the submucous coat and establish itself there. 

 Before this happens, however, the metachromatinic grains of the 

 spore disappear, and it is suggested that this disappearance is related 

 to the secretion of the sarcocystine, and that the toxin is contained 

 in the metachromatinic grains. If, however, a polar capsule be 

 discharged during the germination of the spore, as in other Cnido- 

 sporidia, it might well be that the toxin is contained in the polar 

 capsule and is set free by its discharge, like the poison in the neniato- 

 cysts of the Ccelentera. However that may be, it would appear as 

 if the sarcocystine were a weapon, as it were, the function of which 

 is to facilitate the invasion of the germ, the amcebula, by destroying 

 the lining epithelium of the gut. 



The liberation of the amoebula from the spore initiates the first 

 period of the development, which is passed in the lymph-spaces of 

 the intestine, and which lasts, according to Erdmann, some twenty- 

 eight to thirty days. Analogy with other Neosi)oridia would lead 

 us to identify this with the planont-phase, initiated, possibly, by 

 sexual processes between different aracebuUe and subsequent active 

 multiplication. The second period of the development begins with 



