488 THEOPHILUS S. PAINTER 



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 Zeitschr. f. Phys. Chem., vol. 70. 



Wastase, S. 1893 On the homology of the centrosome. Jour. Morph., vol. 8. 



Wilson, C. B. 1900 The habits and early development of cerebratulus lacteus. 

 Quart. Jour. Mic. Sci., vol. 43. 



Wilson, E. B. 1895 Archoplasm, Centrosome and Chromatin in the Sea Ur- 

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 vol. 12. 



1901b Experimental studies in cytology. Arch. f. Entw. Mech., 

 vol. 13. 



Ziegler, H. E. 1898a Experimentelle Studien ueber die Zelltellung. II. 

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explanation of plates 



Owing to the fact that this study has been made at different places, the draw- 

 ings are not all of the same magnification. All the drawings up to and including 

 figure 26, plate 4, were made, or completed, by Miss L. Krause of the Osborn 

 Zoological Laboratory, Yale University, New Haven, Conn. 



PLATE 1 

 EXPLANATION of figures 



All drawings, with exception of 1 and 2, are from free hand sketches 

 of Strongylocentrotus eggs. 



1. Camera sketch of egg showing swelling of the hyaline layer. 



2 to 5 Various stages of the protoplasmic movement in monaster eggs. Fig- 

 ure 2 is from a camera drawing. 



6 Protoplasmic movement of second division cycle. 



7 and 8 Dividing monaster eggs. 

 9 Disintegrating monaster egg. 



