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 zodlogies 
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 6, and then bursts, discharging 
its protoplasmic contents, as seen at ¢ and d. This in a 
few minutes lengthens out and produces at one end a hair- 
like czliwm, 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 
