4 MANUAL OF ZOOLOGY. 



inseparably connected with organisation. In point of fact, no 

 rigid definition of life appears to be at present possible, and it 

 is best to regard it as being simply a tendency exhibited by 

 certain forms of matter, under certain conditions, to pass 

 through a series of changes in a more or less definite and 

 determinate sequence. 



As regards the connection between life and organisation, 

 it appears that whilst all organised bodies exhibit this ten- 

 dency to change, and are therefore alive, all living beings are 

 not necessarily organised. Many of the lowest forms of life 

 (such as the Foraminifera amongst the Protozoa) fail to fulfil 

 one of the most essential conditions of organisation, being de- 

 void of definite parts or organs of any kind. Nevertheless, they 

 are capable of manifesting all the essential phenomena of 

 life ; they are produced from bodies like themselves ; they eat, 

 digest, and move, and exhibit distinct sensibility to many ex- 

 ternal impressions. Furthermore, many of these little masses 

 of structureless jelly possess the power of manufacturing for 

 themselves, of lime, or of the still more intractable flint, 

 external shells of surpassing beauty and mathematical regu- 

 larity. In the face of these facts we are therefore compelled 

 to come to the conclusion that life is truly the cause and not 

 the consequence of organisation ; or, in other words, that or- 

 ganisation is not an intrinsic and indispensable condition of 

 vital phenomena. 



Such an intrinsic and indispensable condition is, however, 

 according to Huxley, to be found in the presence of a uniform 

 " physical basis," to which he has applied the name of "pro- 

 toplasm," (the "bioplasm" of Dr Beale). Without such a 

 material substratum, or medium upon which to work, no 

 one vital phenomenon can be exhibited. The necessary 

 forces may be there, but in the absence of this necessary 

 vehicle there can be no outward and visible manifestation 

 of their existence. Life, therefore, as we know it, and as far 

 as we know it, may be said to be inseparably connected with 

 protoplasm. 



As regards its nature, protoplasm, though capable of form- 

 ing the most complex structures, does not necessarily exhibit 

 anything which can be looked upon as organisation, or dif- 

 ferentiation into distinct parts ; and its chemical composi- 

 tion is the only constant which can be certainly stated. It 

 consists, namely, in all its forms, of the four elements, carbon, 

 hydrogen, oxygen, and nitrogen, united into a proximate 

 compound to which Mulder applied the name of " proteine," 

 and which is very nearly identical with albumen or white-of- 



