504 Existence of Cell Communications between Blastomeres. 



Against either Meyer's or Sedgwick's theory, cases can he cited of cells in 

 the body, as the blood cells, the mesenchyme of many Invertebrates, which 

 are quite free ; but perhaps the force of these and similar facts is removed 

 when we consider that fixed and specialised tissue cells, such as the squamous 

 epithelium of the cornea, are capable of assuming the character of leucocytes 

 and wandering free as the response to injury. Certainly in view of all the 

 evidence that has been gradually accumulating, our conception of the cell 

 theory needs remodelling on some such lines as Meyer has laid down. This 

 has clearly been pointed out by Sedgwick (10) and Whitman (14). In the 

 words of Sachs (8) cells are " merely one of the numerous expressions of the 

 formative forces which reside in all matter." 



LITERATUEE. 



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' Jen. Zeitschr. f. Naturw.,' vol. 23, pi. 24, pp. 389—412, 1889. 



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vol. 174, 1883. 



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6. Klaatsch, H. " Die Intercellularstrukturen an der Keimblase des Amphioxus," 



' Sitzber. k. preuss. Akad. Wiss.,' Berlin, 1898. 



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8. Sachs, J. " Lectures on the Physiology of Plants." 



9. Schiiberg, A. " Untersuchungen uber Zellverbindungen," ' Zeit. f. Wiss. Zool.,' 



vol. 74, pp. 155—325, 1903. 



10. Sedgwick, Adam. " On the Inadequacy of the Cell Theory," ' Q. J. M. S.,' vol. 37, 



p. 87, 1894. 



11. "The Development of the Cape Species of Peripatus, Part II," 'Q. J. M. S., 1 



vol. 27, 1886. 



12. Townsend, C. O. " Der Einfluss des Zellkerns auf die Bildung der Zellhaut," ' Jahrb. 



"Wiss. Bot.,' vol. 30, 1897. 



13. Treadwell, A. "The Cytogeny of Podarke obscura, Verrill," 'Journ. Morph.,' 



vol. 17, pp. 399—476, 1901. 



14. Whitman, C. O. ' The Inadequacy of the Cell Theory of Development,' Woods Holl 



Biol. Lect, 1893. 



15. Wilson, E. B. ' The Cell in Development and Inheritance,' 2nd edit., New York, 



1900. 



16. " Amphioxus and the Mosaic Theory of Development," ' Journ. Morph.,' 



vol. 8, p. 595, 1893. 



17. "On Protoplasmic Structure in the Eggs of Echinoderms and some other 



Animals," 'Journ. Morph.,' vol. 15, Suppl., p. 1, 1899. 



