AND FACTORS WHICH INFLUENCE THEM. 139 



sphere, may modify the spherical tendency of the highly plastic 

 plasm of rising sporangia. 



Other modifying influences are the ingredients of the plasmodia 

 producing the sporangia. These may be roughly classified as 

 colloids, colloidal solutions, and suspensoids. The purer colloids 

 constitute the essential plasm, the living substance which divides 

 into spores after being relieved of its impedimenta. The colloids 

 in solution are albuminous refuse resulting from metabolism. 

 In the developing sporangia, they gelatinise into pellicles, or 

 coagulate into cartilaginous membranes either at interfaces or 

 exteriors, where they are trapped by the surface tension and so 

 concentrated. The suspensoids are particles of mineral or 

 vegetable substances, gathered up by the plasmodia in their 

 amoeboid wanderings and held in more or less stable suspension 

 until deposited owing to concentration, or to being trapped, like 

 the refuse colloids, at surfaces or interfaces. These particles 

 are mainly of a calcareous or cellulose nature, and furnish 

 materials of which the supporting structures, viz. stalks, colu- 

 mellae and capillitia, are chiefly composed. 



To the interaction of these varying factors we must add 

 capillary effects due to watery condition of the plasm, also 

 effects of gravitation and of any lateral pressure there may be 

 by reason of congested surroundings. Desiccation likewise gives 

 rise to many and often strange distortions, owing to unequal dis- 

 tribution of impedimenta in the plasm, and consequent unequal 

 shrinkage in drying. Putting all these considerations together, 

 we see that sporangial forms are functions of many variables, 

 and that the diversified results exhibited after desiccation and 

 rupture of sporangia walls are scarcely to be wondered at. We 

 already perceive that " quite simple combinations of well-known 

 forces lead to the performance of complicated and apparently 

 purposeful results." The results are indeed manifold, but the 

 purposes we read into them are usually imaginary. 



To establish the proposition that sporangia of Mycetozoa 

 when not actually spherical are to be regarded as globular forms 



JouRN. Q. M. C, Series II.— No. 79. 11 



