A. E. HILTON ON THE LIFE-PHASES ON MYCETOZOA. Ot 



can these constantly recurring forms, often very beautiful, be 

 regarded as of only secondary concern ? The answer is clear. 

 Details which are iTseful enough for classification purposes are 

 often of little importance in biology ; and in the case of Mycetozoa 

 the characters at present relied upon for classification are features 

 of death rather than phases of life. They are, in fact, but the 

 ^.lead casts and perishing excreta of the plastic substance which 

 <leposited them while passing on to its next phase. 



JFor example, on the spores, which to the eye look like fine 

 powder, and also on the very fine threads or fibres known as 

 capillitia, among which the spores are usually embedded in the 

 sporangia, there are markings so delicate as frequently to re- 

 quire a yV-inch objective to make them out distinctly. These, 

 with other more visible characteristics, are the best basis of 

 classification yet discovered. But that these are not living 

 characters becomes evident when the spores escape from the 

 sporangia and the plasm-specks escape from the spores, for 

 then the lifeless threads and broken spore-cells, with all their 

 <lelicate sculpture, are left to decay. 



It is certain, of course, that these microscopical details of the 

 -spores and capillitia are profoundly significant of somethings 

 otherwise they would not recur with suflicient regularity to 

 farnish any basis of classification whatever. Obviously the 

 constitutional differences which distinguish the plasm of one 

 species from that of another have their inevitable effect, and 

 leave their distinctive stamp upon the by-products of the or- 

 ganism ; but that is a problem of physics rather than biology, 

 because it involves the deeper question of the constitution of 

 all matter, living or dead. 



Keturning to our study of the plasm, which presents in an 

 extraordinary degree the opj^osite and alternating phenomena of 

 fusion and division, regulated by conditions of moisture and dry- 

 ness, we notice, in the next place, an alternation of another 

 kind, connected with the food-supply. The plasm passes through 

 periods of assimilation, causing grow'th, but leading to congestion 

 and sluggishness ; and such periods alternate with times of 

 elimination of undigested substances, and consequent recovery 

 of energy. Beginning with the sw^arm-spores, which apparently 

 feed on bacteria, and probably also on other substances in 

 solution, assimilation is carried on during the miscellaneous 



