PROTOPLASM AND ITS PROPERTIES 179 



is found in the slime moulds, which live upon rotten tan 

 bark, decaying wood, and so on. These curious organ- 

 isms have so many of the characteristics both of animals 

 and of plants that they have been described in zoologies 

 under the former title and in botanies under the latter 

 one. Perhaps it would not really be so absurd a state- 

 ment as it might seem, to say that every slime mould leads 

 the life of an animal during one period of its existence and 

 of a plant at another period. At any rate, whatever their 

 true nature, these little masses of unenclosed protoplasm 

 illustrate admirably some of the most important properties 

 of protoplasm. Slime moulds spring from minute bodies 

 called spores (Fig. 125, a) which differ from the seeds of 

 seed-plants not only in their microscopic size but still 

 more in their lack of an embryo. The spores of slime 

 moulds are capable, when kept dry, of preserving for 

 many years their power of germination, but in the pres- 

 ence of moisture and warmth they will germinate as soon 

 as they are scattered. During the process of germination 

 the spore swells, as shown at 5, and then bursts, discharging 

 its protoplasmic contents, as seen at c and d. This in a 

 few minutes lengthens out and produces at one end a hair- 

 like cilium, as shown at e,f, g. These ciliated bodies are 

 called swarmspores, from their power of swimming freely 

 about by the vibrating motion of the cilia. Every swarm- 

 spore has at its ciliated end a nucleus, and at the other end 

 a bubble-like object which gradually expands, quickly dis- 

 appears, and then again expands. This contractile vacuole 

 is commonly met with in animalcules, and increases the 

 likeness between the slime moulds and many microscopic 

 animals. The next change of the swarmspores is into an 



