1914.] NATURAL SCIENCES OF PHILADELPHIA. 433 



the penetration of the amcebula into a muscle-fiber, in which the 

 parasite grows into a Miescher's tube and forms spores." 



The present writer has for some time been in possession of material 

 which illustrates the earlier stages of the cycle of Sarcocystis muris 

 in the mouse, but sufficient time has not been available completely 

 to work out this cycle in all of its details. Since,ihowever, Erdmann's 

 conclusions are largely erroneous, and since, moreover, they are 

 becoming incorporated into general works on the Protozoa, it has 

 been considered desirable to publish a brief notice giving the essen- 

 tial facts discovered, which are of considerable theoretical interest. 

 A short note bearing on this matter w^as published in Science (1913, 

 n. s., V. 37, p. 498) last year, but this did not touch upon the more 

 important of the discoveries made'. 



As stated in the note which appeared in Science, the spore when 

 in the lumen of the intestine of the mouse does not set free an amoe- 

 bula, since it is itself a naked mass of protoplasm. What actually 

 takes place is that the spore, when in the intestine of the mouse, 

 becomes endowed with the ability to display very energetic twisting 

 and boring movements, by virtue of which it forces its way into a 

 cylinder cell of the intestinal epithelium, and there comes to rest. 

 This takes place within 2h hours after the infecting feed, and possibly 

 much earlier. 



The typical spore of Sarcocystis niuris, which has been figured a 

 number of times in the literature, is a banana-shaped organism about 

 12/^ long. Spores of this sort are found both free in the lumen and in 

 the cylinder cells in mice killed and examined at appropriate periods 

 after the inoculative feed. Besides these, however, others occur, such 

 as are shown in Plate XV, figs. 1 and 2. These are oval bodies, 

 generally about half as long as the typical spore. The cytoplasm 

 has a considerable affinity for chromatin stains and consists of a 

 dense spongioplasm. The nucleus is vesicular and more conspicuous 

 than it is in the typical spores. It apparently always contains either 

 a feebly developed nuclear net (fig. 3) or a karyosome or both, but 

 these last-named structures require heavy staining for their demon- 

 stration, and in moderately or lightly stained material the appearance 

 is as shown in figs. 1 and 2. 



Figures 2 and 3 represent conditions found in a mouse killed about 

 2\ hours after feeding. Since, however, the spores in the lumen of 

 the intestine of this mouse are in precisely the same state as those 

 illustrated in fig. 2, the presumption is that these latter have only 

 been in the cells a very short time. Moreover, the intracellular 



