156 THE BEGINNINGS OF LIFE. 



spect. As previously mentioned ^, Leptomhus pro- 

 duces motionless reproductive corpuscles, whilst the 

 protoplasm in the almost similar terminal chambers 

 of Achlya produce active spores (^ zoospores '), which 

 after a time become stationary and develop filaments 

 similar to those from which they have been derived. 

 The reproductive units of other Fungi {Mycetoz,oa) 

 appear as Amoebae, which after a time themselves take 

 on the characters and mode of growth characteristic of 

 a fungus. And finally, each of these forms (Amoeba and 

 Monad) which is thus related to the common form 

 (Fungus), has been proved by many observers to be 

 easily interchangeable with the other. Encysted Amoebx 

 as we have learned from Haeckel, and others, give 

 birth to flagellated Monads or ^ zoospores,' and these in 

 their turn lapse easily into the more slowly-moving 

 reptant Amoebae. Similar transitions, moreover, from 

 the active flagellated Monad, to the slowly- moving 

 vacuolated Amoeba, I have seen dozens of times, whilst 

 watching these forms under high microscopic powers, in 

 various infusions. I have also seen numbers of simple, 

 motionless corpuscles, resembling some forms of Torul^.^ 

 gradually begin to take on amoeboid characters and 

 movements 2. 



Facts of this kind, even independently of those 

 which will be subsequently adduced ^, tend to reveal 



^ See vol. i. p. 182, note i. 

 2 See Fig, 55. 

 ^ In Chap. xvii. 



