710 



from which the implantate had been derived and that the direction 

 of tlie movement was determined by the origin of the inipiantale, 

 not by the new surroundings (a true case of "Seibstdifferenzierung" 

 after Roux). 



Now it may justly be assumed tiiat in the younger stages that 

 I operated upon, tiie implantates are readily taken np into organic 

 (connection with their surroundings. In experimental embryology 

 numerous cases are known in which sncli an implantate behaves 

 in every respect like the region it lins displaced. Nay, the fact that 

 the implantate is competent to incite remote cells to display their 

 organogenetic function, points indeed to conduction of a stimulus 

 from the implantate to its environment, which also implies that the 

 implantate has an organic relation with its enviionment. 



In order to account for the beautiful metachronism in the ciliary 

 movement it is generally supposed that there is a conduction of 

 stimuli from one ciliated cell to the other. Recent experiments by 

 WiNTREBEHT ') have proved, moreover, that this conduction exists 

 and takes place in young stages without the help of the nervous 

 system, i.e. in the epitlielium alone. 



The experiments on blastulae and young gastrnlae go to show 

 that the turned patches vibrate co-ordinately with their environment. 

 This implies that not only the direction of the movement of every 

 cell is opposite to that in which the cell would originally have 

 moved, but also that the regulation of the ciliary movement is 

 reversed and agrees with the sequence of vibrations in the environ- 

 ment of the rotated patch. 



This co-ordinate movement simultaneous with the environment 

 proves: 1° that the patch is apparently stimulated by the environ- 

 ment (so that the conduction of stimuli has not been interrupted); 

 2° that the polarity of the cell is reversed; 3° that the direction of 

 the stimulus-conduction is reversed. If in an older larva a patch of 

 epidermis is turned, then the cilia on this patch persist in moving 

 co-ordinately, but not in co-ordination with the environment. There 

 is not a single reason why the patch should not receive stimuli 

 from its environment now. Various experimental embryoiogical data 

 point to the fact that also in these stages such a relation arises 

 again after the wounds have been healed. If this is the case, the 

 results of the experiments with older stages would imply 1° that 

 then the polarity of the cell is not reversed ; 2' that the conduction 

 of the stimuli still takes place in the original direction. 



1) P. WiNTREBERT. Gomptes reiidus de I'Acad. des Sciences, t'aris T. 172. 19!21, 

 p. 934. 



