1S93.] ^^ [Hubbard. 



St. George, Valette : '92. Ueber iunere Zwitterbildung beim Fluss- 

 krebs. Arkiv. fiir Mikro. Anat., Vol. xxxix, Taf. xxi. 



ScHUTZ, Joseph: '82. Ueber den Dotterkern, dessen Entatehung, Struc- 

 tur, Vorkommen, und Bedeutung. Bonn, 18S2. 



Thompson : '59. * Abstract in "Die Entwick. der Unke." By Alexan- 

 der Goette. P. 8. Leipzig. 



Van Bambeke, C. H.: '70. * Abstract in "Die Entwick. der Unke." By 

 Alexander Goette. P. 9. Leipzig. 

 '83. Contributions a I'histoire de la constitution de I'ceuf. 

 Brussels, 1883. Extrait du Bulletin de I'Academie royale des sciences 

 de Belgique. 52 annee, 3 serie, tome vi, No. 12. 



Zeller, Ernst: '91. Berichtigung, betreffend die Samenaufnabme der 

 weiblichen Tritonen. Zeit. fiir Wissen. Zool., Vol. li, Taf. xxxvi. 



Explanation of Figures. 

 Abbreviations, 

 b — blastoderm, 

 /—follicle. 



m — egg membrane = zona radiata. 

 nl — nucleus. 

 yA— yolk. 

 z — zona radiata. 

 yk. nl. — yolk nucleus. 



All the figures were drawn with the Abbe camera and Zeiss D and 4 ,«, 

 x330. 



Figs. 1-9 and 24-26, inclusive, are found on Plate i. 

 " 10-18, inclusive, are found on Plate ii. 

 " 19-23, " " " " iii. 



Fig. 1. First appearance of yolk nucleus in smallest eggs. 

 " 1(a). Nucleus before extrusion of yolk nucleus. 

 " 2,3. Successive stages of growth. 

 " 4. Yolk nucleus mucb reduced in size. 



" 5-16. Successive changes in appearance and growth of the yolk 

 nucleus. 

 (All of the above eggs stained in hgematoxylin.) 

 "17(o),18. Stained in eosin. 

 " 19. Egg near the time of maturation. 

 Fig. 20. A little latter stage than that of Fig. 19. 

 " 21. A ripe egg. Yolk collected at entodermic pole of the egg. 

 " 22. Egg segmented into 2 cells. 

 "23. " " " 32-64 cells. 



" 24. " " " many cells, probably 600. 



" 25. Late stage in segmentation. Blastopore nearly closed. 

 " 26. Blastopore closed. Yolk nucleus somewhat scattered through 

 the yolk. 



