144 RESEARCHES ON FUNGI 



of rods moving upwards on one another continually leaves be- 

 hind and below it an external layer at its base which has become 

 sUghtly hardened by exposure to the air and is composed partly of 

 the gelatinous matrix and partly of individuals which soon become 

 indistinguishable in it." After a time, under suitable conditions, 

 the cysts are able to "germinate" (Fig. 80, D) : the bacterial 

 contents of each cyst leave the cyst wall as an empty shell, the 

 escaped individual rods then divide rapidly, and thus is initiated 

 a new period of vegetative activity. Social organisation in 

 Chondromyces crocatus is therefore exhibited in two ways : 



Fig. 77. — Hydrodictyon utricidatum, known as the Water-net, a 

 green fresh-water plankton alga. The net, shown natural size, 

 is composed of cylindrical cells, each of which was once a swarming 

 biciliate zoospore. The net is therefore of colonial origin. After 

 Cohn, from Bennett and Murray's Handbook of Cryptogamic 

 Botany (1889). 



(1) in that, in the building up of the fructification, to use the 

 words of Thaxter,^ " there is a concerted action of aggregates of 

 individuals toward a definite end, namely, the production of 

 a more or less highly differentiated resting state " ; and (2) in 

 that the bacteria which happen to be enclosed in a stalk dur- 

 ing its formation are sacrificed for the welfare of the bacteria 

 enclosed within the cysts, only the latter serving to reproduce the 

 species. 



The Acrasieae. — In Dictyostelium mucoroides (Fig. 82, A and B), 

 one of the Acrasieae, social organisation is even more advanced 

 than in the Myxobacteriaceae. In this species, as was first observed 



1 R. Thaxter, " On the Myxobacteriaceae, a new order of Schizomycetes," 

 Botanical Gazette, vol. xvii, 1892, p. 392. 



