FIELD NATURALISTS' CLUB. 33 



2. Merismopedia. These are also called plate cocci from the 

 fact that they divide in two directions forming lamella: or plates. 



Most of the members of this genus are saprophytic. One 

 species, Micrococcus tetragonus, found in tubercular cavities and 

 sputum is saprophytic in man, but pathogenic in the lower 

 animals, causing death in guinea pigs and mice in from two to 

 ten davs. 



.'). Sarcina. The genus Sarcina is characterized by division 

 in three directions forming colonies in cubes or packets. Hence 

 these are called packet-cocci. 



They are all unassociated with disease. The best known is 

 the Sarcina venfriculi described by Goodsir of Edinburgh in 

 1842. These cocci occur in groups of four or multiples of four 

 producing packets with rounded off corners like bales of cotton. 

 They are found in the stomach of man and animals in health and 

 disease. 



4. Micrococcus. This genus is characterized by division in 

 one direction. The cocci after division may remain aggregated 

 in irregular heaps, and are therefore called mass cocci. They 

 never form chains. 



There are several species of micrococcus and some of them 

 are found associated with scarlet fever, measles, whooping cough 

 and other diseases in man, but none of them have ever been 

 proved to be the cause of these diseases. Koch however, has 

 shown that certain micrococci produce septicaemia, pyaemia and 

 progressive suppuration in rabbits, and Klein has described a 

 coccus which gives rise to pyaemia in mice. 



5. Ascococcus. The individual cocci are like micrococci, but 

 they grow in characteristic gelatinous pellicles, and are hence 

 called pellicle-cocci. 



Only one species is known, Ascococctis billrothii. On the 

 surface of nutrient media these cocci form a cream-like skin, 

 made up of an enormous number of globular or oval families, 

 each of which is surrounded by a thick capsule of cartilaginous 

 consistency. 



Group II. Bacteriacea\ 



This group possesses mostly cocci, straight or bent rods, and 

 straight or spiral thread-forms. The cocci may be absent. The 

 thread-forms present no difference between base and arex. 

 Fission occurs only in one direction. 



There are six genera in the group, 



1. Bacterium. This genus is characterized by cocci and reds 

 or only rods, which are joined together to form threads. Sprie 

 formation is absent or unknown. The absence of spore formation 

 is now used to distinguish bacteria from bacilli. The arbitrary 



