GENERAL ORGANIZATION 765 



Crawley (1916) gives an account of the early stages of development of 

 the spore in the intestine of mice. He supposes that the spores first 

 differentiate in the lumen of the gut into male and female forms. These 

 enter the epithelial cells and undergo further changes. The nucleus of 

 the male enlarges and its cytoplasm disappears entirely. The nucleus is 

 then supposed to produce microgametes, as in coccidia. The female, 

 however, retains its cytoplasm, and is eventually fertilized by a micro- 

 gamete. Crawley supposes that the zygote so formed proceeds to multiply 

 in the cell, as Erdmann has described. The description given by Crawley 

 seems very unconvincing, and some of his figures might equally well 

 represent degenerating parasites, while others might conceivably be stages 

 in the development of Eimeria falciformis, which is a common intestinal 

 parasite of mice. According to Marullaz (1920), in mice which have been 

 fed on infected material the spores can be found in the intestinal cells 

 within two hours. Soon after this they become round and the nucleus 

 divides by mitosis. Finally, division into two takes place. The daughter 

 forms may escape into the intestine again and infect other cells. Mul- 

 tiplication by binary fission goes on for about ten days. Meanwhile, 

 parasites have been entering the lymphatic spaces of the villi, and thence 

 make their way to the liver and spleen, where the author found them on 

 the eleventh day after feeding. These forms measure 3 by 4 microns, 

 and have a single nucleus. From the forty-fourth to the fifty-fifth day 

 similar forms were found in the muscle fibres. In addition, certain parasites 

 in the muscles had two nuclei, and in one case there appeared to be a 

 division into eight cells. The author regards the last named as an early 

 stage in the development of a typical sarcocyst. Arai (1925) fed mice with 

 spores of S. tenella of sheep. He noted that, during the first three hours, 

 the spores could be found in all parts of the intestine, but only those in the 

 upper parts of the small intestine were unchanged in appearance. Those 

 occurring lower down were evidently in a degenerate or dying condition. 

 The unchanged spores high up in the intestine during the three hours 

 following the feed applied themselves to the surface of the epithelium, 

 passed in between the cells, but not into them, and appeared finally in the 

 subepithelial tissue. Within six hours of feeding all spores had dis- 

 appeared from the lumen of the intestine, while they could not be detected 

 in the subepithelial tissues later than four hours after feeding. On one 

 occasion a spore was found in blood taken from the tail five hours after 

 feeding, and on two occasions in the heart blood six hours after feeding. 

 Between this time and the appearance of young parasites in the muscle 

 fibres thirty-five to fifty days later the spores were not traced. It seems 

 to be an undoubted fact that in the case of the mouse the spores penetrate 

 the intestinal wall, but it is an exceedingly difficult matter to trace such 



