LITERATURE. 47 



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

 each other, but not united, and 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. 



LITEBATUEE. 



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. Mviseum 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. Soi. Vol. XVIII. 1878, 

 p. 109. 



Bambeke. Eecherches sur I'Embryologie des Batraoiens. Bull, de I'Acad. 

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



JBeneden, Ed. van, et Charles Julin. Observations .'ur la maturation, la 

 f^oondatiou et la segmentation de I'oeuf chez les cheiropt^res. Archives 

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



Seneden, E. van. La maturation de I'oeuf, la fficondation, etc., des mammi- 

 fferes. Bull, de I'Acad. roy. Sci. de Belgique. 2me s6r. T. XL. Nr. i2. 

 1875. 



Beneden, E. van. Contributions &, I'histoire de la v^sicule germinative, etc. 

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



Beneden, E. van. Eecherches sur la maturation de I'oeuf, la f^oondation et 

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



Beuedeu, van, et ITeyt. Nouvelles recherohes sur la f^condation et la 

 division mitosique chez I'Asoaride m6galoc6phale. Leipzig 1887. And 

 Bull, de I'Acad. roy. Sci. de Belgique. 3me s6r. T. XIV. p. 215. 



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

 tralblatt. Bd. VIL 1887. 



Blochmiaun, Ueber die Riohtungskorper bei Insecteneiern. Morphol. Jahrb 

 Bd. XII. 1887, p. 544. 



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

 schrift zur Feier des SOOjahr. Bestehens der Univ. Heidelberg. 1886. 

 Med. Theil. 



