294 CELL-DIVISION AND DEVELOPMENT 



the general truth of this view has been in certain cases conclusively 

 demonstrated by experiment. 1 It has, however, become clear that 

 this conclusion can be accepted only with certain reservations ; for 

 as development proceeds, the cells may acquire so high a degree 

 of independence that profound modifications may occur in special 

 regions through injury or disease, without affecting the general equi- 

 librium of the body. The most striking proof of this lies in the 

 fact that grafts or transplanted structures may perfectly retain 

 their specific character, though transferred to a different region of 

 the body, or even to another species. Nevertheless the facts of 

 regeneration prove that even in the adult the formative processes in 

 special parts are in many cases definitely correlated with the organ- 

 ization of the entire mass ; and in the following chapter we shall see 

 reason to conclude that such a correlation is a survival, in the adult, 

 of a condition characteristic of the embryonic stages, and that the 

 independence of special parts in the adult is a secondary result of 

 development. 



LITERATURE. VIII 



Berthold, G. Studien liber Protoplasma-mechanik. Leipzig, 1886. 



Boll, Fr. Das Princip des Wachsthums. Berlin, 1876. 



Bourne, G. C. A Criticism of the Cell-theory ; being an answer to Mr. Sedgwick ? s 



article on the Inadequacy of the Cellular Theory of Development : Quart. 



Journ. M. S., XXXVIII. i, 1895. 

 Errara. Zellformen und Seifenblasm : Tagebl. der 60 Versammlung deutscher 



Naturforscher und Aerzte zu Wiesbaden. 1887. 

 Hertwig, 0. Das Problem der Befruchtung und der Isotropie des Eies, eine 



Theorie der Vererbung. Jena, 1884. 



Hofmeister. Die Lehre von der Pflanzenzelle. Leipzig, 1867. 

 McMurrich, J. P. Embryology of the Isopod Crustacea: Journ. Morph., XI. I. 



1895. 



Mark, E. L. Limax. (See List IV.) 

 Rauber, A. Neue Grundlegungen zur Kenntniss der Zelle: Morph. Jah?'b.,V\\\. 



1883. 



Sachs, J. Pflanzenphysiologie. (See List VII.) 

 Sedgwick, H. On the Inadequacy of the Cellular Theory of Development, etc. : 



Quart . Journ . Mic. Sci. , X XX V 1 1 . 1 . 1894. 

 Strasburger, E. Ueber die Wirkungssphare der Kerne und die Zellgrosse : Histo- 



logische Beit rage, V. 1893. 

 Watase, S. Studies on Cephalopods ; I., Cleavage of the Ovum : Journ. Morph., 



IV. 3. 1891. 

 Whitman, C. 0. The Inadequacy of the Cell-theory of Development : Wood's Holl 



Biol. Lectures. 1893. 



Wilson, Edm. B. The Cell-lineage of Nereis: Journ. Morph., VI. 3. 1892. 

 Id. Amphioxus and the Mosaic Theory of Development: Journ. Morph., VIII. 



3. 1893. 



*Cf.p. 312. 



