THE SPIRAL TYPE OF CLEAVAGE. 265 



organism, and which, even when once modeled, may be 

 brought back, like a bit of clay, to the original condition and 

 remodeled into a different form if necessary. And further, 

 the material connection between cell and cell, which occurs so 

 widely, is of the utmost importance, for through this, as I 

 believe, the cell becomes simply a part of the organism, in 

 touch with the whole, influenced by the whole, and exercising 

 in its turn an influence upon the whole. Whether that pecul- 

 iar property cf protoplasm which we know as organization be 

 merely the expression of its chemical and physical structure, 

 or, as Driesch believes ('99), the expression of a mysterious 

 force wholly different from any in the inorganic world, it is the 

 organism the individual, which is the unit and not the cell. 



UNIVERSITY OF CHICAGO. 



LIST OF LITERATURE CITED. 



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Univ. Circ. Vol. xvii, No. 123. 



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 '98a ANDREWS, A. E. Activities of Polar Bodies of Cerebratulus. Arch. 



f. Entivicklungsmechanik d. Organismen. Bd. vi, Heft 2. 

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and Sea-Urchin Eggs. Journ. of Morph. Vol. xii, No. 2. 

 '81 BLOCHMANN, F. Ueber die Entwicklung von Neritina fluviatilis. 



Zeitschr.f. wiss. Zool. Bd. xxxvi. 

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teropoden. Zeitschr. f. wiss. Zool. Bd. xxxviii. 

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cristata, etc. Zobl. Bull. Vol. i, No. 2. 

 '97 CONKLIN, E. G. The Embryology of Crepidula. Journ. of Morph. 



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 '99 CONKLIN, E. G. Cleavage and Differentiation. BioL Lect., delivered 



at Woods Holl, Sessions of 1897 and 1898. 



