SPORES 29 



inflatus is also peculiar in this respect of swelling, for, as its name 

 implies, the cell is much inflated and often two endospores may be 

 found enclosed in one cell. Although usually one or two endospores 

 represent the normal number, sometimes, when the cells become 

 elongated, a large number may be present. In Bac. hirtus, the author 

 has seen elongated individuals packed with endospores (Fig. 45). As 



FIG. 45. Spore formation in Bac. hirtus. 



mentioned above, the formation of endospores has, so far, been observed 

 only in two species belonging to the Coccaceae, viz. Sarcina pulmonum 

 and Sarcina ureae. The development of the endospore has been 

 followed in the latter, and in every particular it agrees with the above- 

 mentioned development in the genus Bacillus. The power of resistance 

 possessed by endospores may be judged by the fact that some, notably 

 those of Bac. subtilis, can stand being placed for six hours in boiling 

 water without being destroyed. 



Structure of the Endospore. The endospore has two coats, the thin 

 inner intine, and the thick outer extine. The latter is usually irregular 



FIG. 46. Spore of FIG. 47. Types of spores. (a) Bac. 



Bac. hirtus. asterosporus ; (b) Sarcina ureae ; (c) Bac. 



ruininatus ; (d) Bac. graveolens, and (e) 

 Bac. fusiformis. 



on its outer surface, the commonest feature being blunt points, one 

 at each end (Fig. 46). The endospores of Bac. asterosporous have 

 elaborate markings, the extine being thrown into ridges and troughs 

 as shown in Fig. 47a, whilst those of Sarcina ureae have six or seven 



