BACTERIA AS PLANTS. 31 



and i5/). Others have regarded the whole bac- 

 terium as a nucleus without any protoplasm, 

 while others, again, have concluded that the dis- 

 cerned internal structure is nothing except an ap- 

 pearance presented by the physical arrangement of 

 the protoplasm. While we may believe that they 

 have some internal structure, we must recognise 

 that as yet microscopists have not been able to 

 make it out. In short, the bacteria after two 

 centuries of study appear to us about as they did 

 at first. They must still be described as minute 

 spheres, rods, or spirals, with no further discern- 

 ible structure, sometimes motile and sometimes 

 stationary, sometimes producing spores and some- 

 times not, and multiplying universally by binary 

 fission. With all the development of the modern 

 microscope we can hardly say more than this. 

 Our advance in knowledge of bacteria is con- 

 nected almost wholly with their methods of growth 

 and the effects they produce in Nature. 



ANIMALS OR PLANTS? 



There has been in the past not a little ques- 

 tion as to whether bacteria should be rightly 

 classed with plants or with animals. They cer- 

 tainly have characters which ally them with both. 

 Their very common power of active independent 

 motion and their common habit of living upon 

 complex bodies for foods are animal characters, 

 and have lent force to the suggestion that they 

 are true animals. But their general form, their 

 method of growth and formation of threads, and 

 their method of spore formation are quite plant- 

 like. Their general form is very similar to a 

 group of low green plants known as Ostillaria. 



