[226] _Centralbl. f. Bakt._, Orig., xlvii, p. 612; see also xlvii, p. 56; lv, p. 373. [227] _Journ. Exptl. Med._, xii, p. 19. According to Erdmann[228] (1910) the Sarcosporidian spore germinates in the intestine of the host, which has recently ingested infected material. The spore liberates its contained toxin--sarcocystin--which acts upon the adjacent intestinal epithelium, whereby the latter is shed, and an amœbula creeps out of the spore. The amœbula is able to penetrate the denuded area and get directly into the lymph-spaces of the submucous coat of the intestine. The first period of development, lasting some twenty-eight to thirty days, is said to be passed in the lymph-spaces of the intestine. Later the amœbula reaches a muscle fibre. Writing in May, 1914, Erdmann[229] records the appearance of small amœboid and schizogony forms six days after infection of the host. Crawley[230] (1913) controverts some of these statements and considers that the Sarcosporidian spore, still sickle-shaped, bores its way into the epithelial cells of the intestine and comes to rest there. The spore then becomes round or elliptical, and peripheral masses of chromatin appear within it, suggesting schizogony. This happens about twelve hours after feeding, and in twenty-four hours the spores appear to have left the intestine. More recently (May, 1914), Crawley[231] considers that there is sexual differentiation among the Sarcosporidian spores, a few hours after their ingestion by the host. [228] _Sitz. Gesell. naturf. Freunde zu Berlin_, p. 377. [229] _Proc. Soc. Exper. Biol. and Med._, xi, p. 152. [230] _Science_, xxxvii, p. 498. [231] _Proc. Acad. Nat. Sci._, Philadelphia, May, 1914, p. 432. Interesting discussions have occurred as to the site of the toxic sarcocystin within the spore. Metachromatic granules occur in the middle of the Sarcosporidian spore (fig. 109), and the toxin may be contained in these grains, as they disappear, according to Erdmann, before the amœbula penetrates the denuded intestinal wall. However, a polar capsule, containing a polar filament, may be present at one end of a Sarcosporidian spore. Laveran and Mesnil described a striated area at the more pointed end of the spore of _S. tenella_, which area they consider to represent a polar capsule. Fantham[232] (1913) found a vacuole-like, polar capsule area in the spores of _S. colii_ from the African mouse-bird. The sarcocystin may be contained in the polar capsule. The nucleus of the spore is generally at the opposite, blunter end. [232] _Proc. Cambr. Philosoph. Soc._, xvii, p. 221. Again, various authors have stated that Sarcosporidian spores may occur in the blood of the host at times. If so, then an intermediate host may be concerned in their transmission. Perrin suggested that Sarcosporidia might be spread by blow-flies and flesh-flies.