40 Dr. F. von Wagner on 



certain relations of the parts to the, whole ; " this corresponds, 

 however, to the stage which the organization lias attained at 

 the time, and is therefore " moreover dependent upon the 

 origin and progress, in short the development of the organi- 

 zation." 



This conception applies in the same degree to embryonic 

 development as to reproduction of animals by fission or 

 gemmation. In both cases the individuality of the animal 

 which is coming into existence shows itself dependent upon 

 the progress of the organic development, as a cohesion of 

 definite relations of the parts to the whole, which becomes ever 

 more and more consolidated concurrently with the organiza- 

 tion. But naturally it is impossible that this cohesion should 

 be a rigid one, the same for all animals — this is proved at 

 once by the exceedingly variable degree to which the regene- 

 rative capacity is expressed ; it will, on the contrary, be 

 extensible within narrower or wider limits. Herein lies the 

 a priori difference between fission and gemmation, as well as 

 every other mode of reproduction, since the former neces- 

 sarily postulates a loose arrangement of that cohesion, more 

 readily dissoluble without injury to the common life; for 

 were this not so the power of fission would be altogether 

 suspended. The individuality of animals undergoing tission 

 must therefore be of a fusible kind, so fusible that a con- 

 tinual change in the cohesion of the parts which form a whole 

 is rendered possible, without occasioning disturbance to the 

 common life. 



Experience proves that in all cases of fission a portion of 

 the original relations existing in the parent form is dissolved, 

 and combines with those which now appear for the first time 

 and which result from the development of new organs by 

 regeneration to form a new unit ; while the remnant of the 

 old relations which is left behind either manifests by itself a 

 unity which is viable or replaces the relations which have 

 been lost by equivalent new formations. Thus, in Microstoma 

 an animal divides in the first place into two individuals, 

 whereby theoiiginal individuality is destroyed and superseded 

 by the two new ones. The latter soon experience the like 

 fate, and with the destruction of their individualities four fresh 

 ones are constituted, and so on. 



It is impossible to raise the objection that perhaps they are 

 quite unimportant and trivial portions which are taken from 

 the original animal and applied to the formation of one of the 

 new individuals, and that therefore the individuality of the 

 other zooid is essentially unchanged, since, indeed, it remains 



