SPORES 35 



it is very probable that a conidium can also elongate directly into a 

 new individual. 



The size of the conidia in the various species which form them 

 is remarkably constant, being about l^ fj, in length and 1 /u. in 

 breadth. 



Gonidia (sing, gonidium). These differ from conidia in their 

 mode of origin, being formed usually by the breaking up of cells, 

 each into a number of smaller ones, which are termed gonidia. 

 Fig. .'5 3a represents a thread of Chlamydothrix hyalina before gonidia 

 formation has set in. Fig. 53b shows the same kind of thread full of 

 gonidia. 



Crenothrix polyspora, one of the iron-bacteria, forms gonidia of 

 two sizes, named respectively macrogonidia and microgonidia, the former 

 being the larger and the latter the smaller ones (Fig. 54). The 

 gonidia are thrust out of the thread and develop each into a new 

 thread by a process of elongation (Fig. 54A). Occasionally they develop 

 whilst still attached to the parent organism. 



In Cladothrix dichotoma, another of the iron-bacteria, the gonidia 

 assume a more highly developed form, for they are comparatively 

 large and each is supplied with a lateral bundle of cilia (Fig. 15). 

 By means of these cilia, the gonidia swim actively away, finally 

 attaching themselves to a suitable support. Here they get rid of 

 their cilia and develop into new threads. 



