582 CELL DIVISION IN EGGS OF CREPIDULA. 



v. Wasielewski, W. 



1902, 1903. Theoretische und Experimentelle Beitrage zur Kenntnis der Amitose, I, II. Jahrb. 



wiss. Bot., XXXVIII, XXXIX. 



Wilson, E. B. 



1894. The Mosaic Theory of Development. Woods Hole Lectures, 1893. 



1896. The Cell in Development and Inheritance. New York. 



1897. Centrosome and Middle Piece in the Fertilization of the Egg. Science, V. 



1900. The Cell, etc. 2d Ed. Id. 



1901. Experimental Studies in Cytology, I. Arch. Entw. Mech., XII. 

 1901. Experimental Studies in Cytology, II, III. Id., XIII. 



1904. Studies on Germinal Localization. Journ. Exp. Zool., I. 



ZlEGLER, H. E. UND V. RATH, O. 



1891. Die amitotische Kernteilung bei den Arthropoden. Biol. Centralb., XI. 



ZlEGLER, H. E. 



1891. Die biologische Bedeutung der amitotischen Kernteilung im Tierreich. Id., XI. 



1895. Untersuchungen iiber die Zellteilung. Verh. deutsch. Zool. Ges. 



1898. Experimentelle Studien uber die Zellteilung, III. Arch. Entw. Mech., VI. 



1903. Experimentelle Studien iiber die Zellteilung, IV. Biol. Centralbl., XVI. 



XIV. EXPLANATION OF PLATES XLIII-LIX. 



All figures represent whole eggs of Crepidula plana, fixed, stained, and mounted in balsam. They 

 were drawn at stage level, with camera lucida, under Zeiss' Apochromatic Horn. Immersion Objective 3 

 mm., Comp. Ocular 4, and represent a magnification of 333 diameters. In the process of reproduc- 

 tion they have been reduced about one-fifth. The polar bodies are in all cases shaded by parallel lines, 

 while the crenated fine which appears in most of the figures represents, somewhat diagrammatieally, the 

 line of yolk spherules surrounding the cytoplasmic area. The spheres (centrospheres) are shown in dotted 

 outline, as are also the cells and nuclei which he at lower levels. Only abnormal eggs are represented, 

 though normal eggs are found in many of the experiments. 







Refekence Lettei 



A, B, C, D 



= Macromeres. 





la-Id 



= 1st set of micromeres. 





2a-2d 



= 2d set of micromeres. 





Za-M 



= 3d set of micromeres. 





4d 



= Mesentomere. 





Am. 



= Amphiaster. 





As. 



= Cy taster. 





Ch. ' 



= Chromatin. 





Ch.V. 



= Chromosomal vesicles. 





End. 



= Endoderm. 





F.C. 



= Follicle cells. 





G.V. 



= Germinal vesicle. 



- 



L. 



= Lobe. 





M. 



= Mesomere. 





Memb. 



= Cell membrane. 





N. 



= Nucleus. 





Nl. 



= Nucleolus. 





9N 



= Egg nucleus. 





<?N 



= Sperm nucleus. 





Pb 



= Polar bodies. 





PCp 



= Posterior cell plate. 





s. 



= Sphere. 





ShG 



= Shell gland. 





S.G. 



= Sphere granules. 





f: 



= Spindle. 





= Velum. 





Y. 



= Yolk. 





Z. 



= Zwischenkorper. 





