FrenzePs Mesozoon Saliiiclla. 467 



lio says (Biol. Cenfriill)!. Inc.. cit. p. 577; X\m. <Si. Mag. Naf. 

 Hist. loc. cit. p. 80) : — ^^ In tlie systematic arrangement of 

 the group (i. e. the Protozoa) we are even obliged, hard 

 though it will be for every modern zoologist, to allow our- 

 selves to be swayed by physiological considerations, since 

 here the purely morphological and embryological foundations 

 are insufficient." In cases in which " unfortunately far too 

 little attention is paid " to a " by no means unimportant 

 difference .... pcrliaps in consequence of the fact that it 

 arises in the first place from physiological conditions only," 

 this does not occur because it would be iiard for a modern 

 zoologist to take physiological considerations into account, 

 but because there are unfortunately still far too many zoolo- 

 gists who arc one-sided in their views, i. e. not modern. It 

 appears to me that precisely the perception that differences of 

 a purely physiological nature exist between organisms, espe- 

 cially unicellular ones, which are not to be distinguished 

 morj)hologically («'. e. anatomically and embryologically), is 

 one of the most important acquisitions in biology; for it 

 teaches us that the most essential differences — at least in ray 

 opinion — between organisms are independent of the degree of 

 development which their organization has attained ; and that 

 protoplasm, or, better, Protoblasts — for independent proto- 

 plasm, without forming any kind of Protoblast or living 

 being (Lebeioesen) , lias no existence at all — is subject to 

 material differences even in the non-organized condition. 



Indeed, we must even arrive at the conclusion — in a manner 

 which 1 will perhaps indicate more closely upon another 

 occasion — that in the non-organized condition there already 

 were at least as many original kinds of Protoblasts as there 

 are to-day keally independent forms of living beings, or, 

 we might say, qualities of life ; probably, however, there 

 were many more. It may be that new qualities of life, in 

 spite of the diversity of gradually developing forms of life, 

 did not subsequently come into existence at all; for new and 

 different FORMS OF life may arise by gradual change of shape 

 from apparently similar QUALITIES OF life, the difference 

 between which, though present from the beginning, does not 

 become perceptible until a higher grade of development is 

 reached. Yet it is probable that the qualities of life which 

 were originally present cannot all have sustained the struggle 

 for existence until now. 



More or less visible gulfs between the various forms of life 

 are and must be present, therefore, if we would in any way 

 identify the idea of difference with that of a gulf. The 

 apparent size of such a gulf may in the first instance depend 



35* 



