34 THE CELL 



number of plants, are evidently of a similar nature. Townsend, finally, 

 has not only observed the occurrence of a transmission of nuclear 

 stimuli by means of protoplasmic threads, but has actually shown by 

 experiment that such threads may serve to convey the influence of a 

 nucleus to non-nucleated masses of cytoplasm. Similarly nuclear 

 influences may be transferred from one cell to another through the 

 protoplasmic connecting-threads which traverse the intervening wall. 

 None of these facts, however, in any way detract from the importance 

 that should be attributed to the controlling action which the nucleus 

 can exert at close range. Pfeffer is no doubt justified in comparing 

 the transmission of nuclear influences to the action of a telephone 

 " which enables communications and orders to be repeated at a great 

 distance from their original source " ; nevertheless it cannot be denied, 

 that commands and messages will be transmitted from master to 

 servant with the greatest ease and with the smallest risk of confusion, 

 when the two parties to the transaction are standing face to face. 



The dominating influence exerted by the nucleus during the develop- 

 ment of the cell has led many physiologists to assume, on insufficient 

 grounds, that this organ similarly controls the entire vital activity of 

 the adult cell. The behaviour of protoplasts which have been deprived 

 of their nuclei shows that this inference is not justified. For it is 

 found that such enucleate masses of protoplasm continue to respire, 

 while protoplasmic streaming, the action of cilia and other movements 

 also persist for some time ; the photosynthetic activity of the chloroplasts 

 is not at first affected, and among Conjugatae the formation of starch 

 is not inhibited, though in the case of Funaria this process does seem 

 to be dependent upon the presence of the nucleus. Very instructive 

 are Gerassimoffs observations upon enucleate cells of Spirogyra and 

 other Conjugatae. In some of Gerassimoff's experiments the enucleate 

 condition arose naturally, owing to the circumstance that on division of 

 a nucleus both daughter-nuclei became enclosed in the same daughter- 

 cell. A similar result can be artificially induced if nuclear division be 

 interrupted, after cell-division has begun, by suddenly cooling the cell. 

 Such enucleate cells always die after a few weeks, although the vital 

 processes enumerated above are carried on in the meantime ; they are 

 also more susceptible to the influence of hostile environmental con- 

 ditions, and seem in particular more liable to be attacked by certain 

 parasitic Fungi. Observations of this kind prove that, while a number 

 of vital processes may in the adult cell be independent of nuclear 

 control, the nucleus nevertheless exerts an important though as yet 

 undefined influence, at this stage also, upon the activities of the cell. 



In what manner stimuli are transferred from the nucleus to the 

 ectoplast and to the other cell-organs, is at present quite unknown. 



