Some Questions which they Suggest. 31 



other pieces of protoplasm of their own species from the 

 apparently similar protoplasm of other species. According 

 to the concurrent testimony of three of the chief observers 

 of these organisms, Cienkowski, De Bary, and Lister, 

 " union never takes place between plasmodia of different 

 species." "Branches of different plasmodia," says 

 Cienkowski, " crawl near one another, and mutually 

 embrace one another, without showing the least trace of 

 any fusion." 



The merging of two protoplasms has been seen under the 

 microscope. " There appeared to be no mutual attraction 

 until the two plasmodia were only separated by a distance of 

 40 p.. When a lobe from one was pushed out towards 

 its companion, the intervening swarm cells were thrust 

 aside, and they came into contact; the hyaloplasm 

 (ectoplasm) of each blended at a single point, and then a 

 stream of granular matter was seen to pass, then with a 

 return flow of the streaming in the layer of the two, 

 the channel was widened, and a gush of its contents 

 poured into the smaller one, when union was com- 

 plete and the system of circulation became common to 

 both." 



It may be permissible to adduce another instance of 

 organisms of a very simple character to illustrate at once 

 the attractive force of members of one species on their 

 fellows, and of the capacity for selection which makes 

 them reject the members of other, though very similar 

 species. The case we are about to mention relates to two 

 species of the genus Cutleria, algae of a low type. 



