vii RESULTS OF SECTION IN BEROE 347 



trolled by them, just as do the " brains " of the intermediate 

 parts in the uninjured animal. 



It is also remarkable that when the Scyphomedusse die gradu- 

 ally the brains with the parts surrounding them remain alive 

 longest Aurelia thus gradually perishes, until at length only 

 eight small fragments containing the nerve-centres are left, 1 

 and in like manner Beroe dies towards the aboral pole which 

 contains the greatest number of nerve-cells. But when I cut out 

 one of the eight antimeres of an Aurelia, containing a marginal 

 body in the middle of its lower edge, its death proceeded 

 in the manner explained by the accompanying figure. 2 It 

 began in the middle and proceeded upwards and 

 downwards, until only the lowest portion con- 

 taining the marginal body remained. And this 

 piece went on diminishing towards the marginal 

 body. 



The results of section in Beroe still more strongly 

 support my hypothesis of the development of vicar- 

 ious nerve-centres. 



The locomotion of the Ctenophora is effected by 

 the strokes of the small paddles formed by the con- 

 crescence of cilia, again a motion which can take 

 place both involuntarily and voluntarily. 



Separated portions of this animal all behave after Fl - 2 - 

 some time exactly like the whole : no difference in the move- 

 ments can be recognised voluntary motion of the paddles 

 is evident even in the fragments. 



Thus certain nerve-cells here also must assume the function 

 of direction. But this occurs the more quickly, as follows 

 from the facts already described, the greater the number of 

 such cells present in the fragment only the polar fragment 



1 Die Medusen, p. 80, et seq. 



2 From Die Medusen, fig. 10, where p. 61, et seq., contain further details of the 

 process of dying. The stalked knob represents the marginal body. 



