I08 BIOLOGICAL LECTURES. 



we may have analogies, but no homology of organs between 

 unicellular and multicellular organisms. 



How sharply the line is drawn in this regard is shown in 

 the scrupulous care with which authors avoid the suggestion 

 of anything comparable to muscle or nerve in the infusorian. 

 The Ehrenberg view of infusorian organization demanded 

 altogether too much, and we have swung to the opposite 

 extreme of thinking that the very idea of such comparison is 

 forbidden by the cell-doctrine. Any suggestion of a possible 

 community of origin between an organ — say the vionth — of 

 such an animal and the corresponding structure of a cellular 

 organism, would be quickly relegated to the lijnbus fatuoruDi. 

 Who dares question the proposition that there can be no 

 morphological identity between an organ formed without cells 

 and one formed with cells } No matter how complete the 

 physiological correspondence, the two things must be assumed 

 to differ toto coclo, as measured by the cell-rule. That is the 

 cell-standpoint. 



While the cell-doctrine has been carried steadily forward, 

 confidence in its all-sufficiency has been somewhat shaken from 

 time to time, and a few cautious protests have been ventured 

 against the complete ascendancy of the cell as a unit of organ- 

 ization. Botanists, among whom in this particular the name 

 of Sachs stands foremost, have led the way to another stand- 

 point, which, in contradistinction to the prevailing one. may 

 be called the organism-standpoint. Among zoologists, Rauber 

 has most boldly and ably defended this pt)int of view; and 

 more recently Wilson has expressed similar views, but with 

 reservations that still ui)hold the cell-standpoint. Driesch, 

 too, obtains experimental proof that "the mode of cleavage is 

 something unessential to the future animal," but still he feels 

 compelled to explain the organism from the cell-standpoint, — 

 that is, he supposes that the organism is determined by 

 correlative differentiation of homodynamous ("omnipotent") 

 cells or nuclei. The position is altogether similar to that of 

 Oscar Hertwig and Wilson. Wilson, however, holds that the 

 cleavage may secondarily acquire a "mosaic" significance, and 

 herein makes a decided advance towards a pre-organization 



