172 



siicli a stiimiliis, liowever, as lias already been demonstrated by 

 Noi.i, (Heterogene Induction, 1892), oan be the canse of a move- 

 ment only if the sensitiveness of this outer layer is unequal at 

 different |)arls. As the vertical position, in tiie said organs, was 

 regarded as the one in which no stimulation took place, it was 

 supposed that the part adjoining the lowest transverse wail was not 

 sensitive. If, however, also the longitudinal growth he induced by 

 the gravitation-stimulus, as we suppose here, that part would have 

 to be on the contrary the most sensitive. 



However this may be, it is sure that there must always exist a 

 certain connection between the position of the place of the greatest 

 (or least) sensitiveness in the statocyst and the direction of normal 

 growth of each organ, so that this, for instance in the cells of the 

 vei'tically-growing stem, must be found at a dilferent place to those 

 of a horizontally-growing rhizome, etc. 



This ought to imply furthei' that when an organ of itself changes 

 its |)Osition, this should he preceded by a shifting of the outer layer 

 of the protoplast inside the cell. The supposition of such a shifting 

 of the outer layer would, however, be inconsistent with the general 

 assumption that this layer is immovable, an hypothesis, it is true, 

 but one which for other reasons, e. g. the existence of the plas- 

 modesms, might be called probable. This inconsistency suggests the 

 query as to whether it is not more probable to assume that the 

 excitable portion of the statocyst forms a separate organ of the cell, 

 which might then lie between the outer layer and the granular 

 protoplasm, but (juite independent from the former. 



This protoplasmic part, which alone should be sensitive to the 

 pressure of the starch-grains, might be termed the "static apparatus" 

 and should be capable of shifting, consequent on some influence 



■H 



The accompanying diagram represents, scliematically, the 



1^ supposed position of the "static apparatus" in the statocyst: 

 Z = cellwaii, H = outer layer, K = granular protoplasm, R = 

 the static apparatus of wliicli, M = the middle-field. 



The unequal thickness of the static apparatus in the drawing 

 serves merely to indicate the local difference in sensitiveness 



R, of this apparatus which should be greatest in llie middle- 

 field. 



from inside or outside, without the outer layer of the protoplast 

 being involved in this movement. Moreover this apparatus should 

 have to be most sensitive in the middle-field, while this sensitiveness 



