142 THE CYTOLOGY AND LIFE-HISTORY OF 



ACTERIA 



x^A^ 



<^».v>$ 



[Reproducfd from the Journal of General Microhiolosy.) 



Fig. 63 

 COLONIES OF STREPTOCOCCI 



1. Long-chained " rough " colony. 



2. Short-chained " smooth " colony. 

 Impression preparations ■ 300. 



H: COLONIES OF STREPTOMYCES 

 (4, lo) 

 The colonics ot strcptoniyccs may logically be considered as single, multi- 

 cellular organisms, in which the functions of the various types of component 

 cell are almost completely specialised. The colony consists of a vegetative, 

 haploid, primary mycehum, upon which arises a reproductive, diploid, 

 secondary mycelium. The condition is snnilar to that which obtains in 

 higher tungi. The spores are specialised distributive cells, and a single spore 

 may give rise to the complete colony. Although fragments of mycelium 

 will grow if they are transplanted, the colony is essentially a unit which 

 remains fixed upon its substrate, so long as the food supply permits, and it 

 reproduces solely by the release of spores. The cells of the mycelium perish 

 when the food supply is exhausted or when conditions become unsuitable for 

 growth. 



Thus, in bacteria, the type of multicellularity represented by the swarm 

 finds its greatest perfection in myxobacteria, the sessile colony in the strep- 

 tomyces. In each the mode of reproduction and distribution is admirably 

 designed to the case. 



