320 ORGANIC GROWTH 



at least in the higher protozoa, in the ciliata, the seat of 

 nervous activity is to be sought principally in the outer layer 

 of protoplasm, and that the will resides in every protoplasmic 

 element, that nervous action is not limited to definite paths. 

 He supports his view by the fact that the movements in the 

 two parts of an Infusorian in process of division exactly 

 correspond so long as they are connected by a strand of 

 protoplasm, however thin (Stentor). The same thing is 

 observed also after incomplete artificial division. This proves, 

 he says, "that the nervous power of the cell is diffused." 

 In the figure given in illustration a Steutor is represented 

 diagramatically as divided transversely, that is, so that the 

 nucleus also is transversely divided. Whether pieces with- 

 out nucleus act voluntarily is not stated. But it would be 

 necessary to determine this. My experiments in dividing 

 Medusae, to be shortly discussed, afford a perfectly analo- 

 gous case, and yet localised cerebral ganglia are certainly 

 present there. If, as I shall endeavour to show, nuclei 

 actually form central nervous organs in multicellular animals, 

 it is evidently highly probable that they do so also in 

 the unicellular. In the cases referred to of multicellular 

 animals in which a circumscribed brain is not yet present, 

 the exertion of will is only to be conceived as proceeding 

 from circumscribed central points (nuclei) which are in 

 connection with one another, and to which the impressions 

 received by the rest of the cell are conveyed. Since all 

 the action of will depends on the employment of impres- 

 sions which must be conveyed to the organ of will along 

 separate protoplasmic conducting paths, therefore the organ 

 of will can scarcely be the whole protoplasm of the body, 

 but rather the very presence of a will implies in itself 



tion of life in snails. Duges and Moquin Tandon obtained this result (cf. Milne- 

 Edwards, Lemons sur la Physiologie et VAnatomie Compare, Tome viii. p. 304), 

 and recently J. Carriere has confirmed it (Studien uber die Regenerationserschein- 

 ungen der Wirbellosen, I. Regeneration bei Pulmonaten, Wiirzburg, 1880. 



