LITERATURE. 47 



nucleus ; in many objects they remain for a considerable time near 

 each other, but not united, arid only later are together metamorphosed 

 into the segmentation-spindle. 



9. In some animals fertilisation of the egg takes place only after 

 completion of its maturation, but in others it is inaugurated at the 

 very beginning of maturation, so that the two phenomena overlap 

 each other. 



10. Fertilisation theory. Fertilisation depends on the copulation 

 of two cell-nuclei, which are derived from a male cell and a female 

 cell. 



11. Theory of heredity. The male and female nuclear substances 

 contained in the spermatic nucleus and the egg-nucleus are the 

 bearers of the peculiarities which are transmissible from parents to 

 their offspring. 



LITERATURE. 



Agassiz and Whitman. The Development of Osseous Fishes. II. The 



pre-embryonic Stages of Development. Pt. 2. The History of the Egg 



from Fertilization to Cleavage. Mem. Museum Comp. Zoology at Harvard 



College. Vol. XIV. No. I. Part II. 1889. 



Balfour. On the Phenomena accompanying the Maturation and Im- 

 pregnation of the Ovum. Quart. Jour. Micr. Sci. Vol. XVIII. 1878, 



p. 109. 

 Bambeke. Eecherches sur 1'Embryologie des Batraciens. Bull, de 1'Acad. 



roy. Sci. de Belgique. 2me ser. T. LXI. 1876. 

 Beneden, Ed. van, et Charles Julin. Observations sur la maturation, la 



fecondation et la segmentation de 1'oeuf chez les cheiropteres. Archives 



de Biologic. T. I. 1880, p. 551. 

 Beneden, E. van. La maturation de 1'oeuf, la fecondation, etc., des mammi- 



feres. Bull, de 1'Acad. roy. Sci. de Belgique. 2me ser. T. XL. Xr. 12. 



1875. 

 Beneden, E. van. Contributions a 1'histoire de la vesicule germinative, etc. 



Bull, de 1'Acad. roy. Sci. de Belgique. 2me ser. T. XLI. Nr. 1. 1876. 

 Beneden, E. van. Eecherches sur la maturation de 1'oeuf, la fecondation et 



la division cellulaire. Archives de Biologic. T. IV. Paris 1883. 

 leneden, van, et TsTeyt. Nouvelles recherches sur la fecondation et la 



division mitosique chez 1'Ascaride megalocephale. Leipzig 1887. And 



Bull, de 1'Acad. roy. Sci. de Belgique. 3me ser. T. XIV. p. 215. 

 Blochmann. Ueber die Eichtungskorper bei den Insecteneiern. Biol. Cen- 



tralblatt. Bd. VII. 1887. 

 Blochmann. Ueber die Eichtungskorper bei Insecteneiern. Morphol. Jahrb 



Bd. XII. 1887, p. 544. 

 Blochmann. Ueber die Reifung der Eier bei Ameisen und Wespen. Fest- 



Ischrift zur Feier des SOOjiihr. Bestehens der Univ. Heidelberg. 1886. 

 Med. Theil. 



