THE CELL DOCTRINE. 135 



jeet have been by Auerbach,* Strassburger,t Hert- 

 wig,:]: and Van Beneden,§ to whom may be added 

 Butschli,|| Oel]acher,T[ Kleinenberg,** and Balfour.ft 

 Under the influence of the fertilizing act the ovnm 

 again becomes nucleated, the nucleus arising in a 

 fusion of pronuclear bodies, one of which may pos- 

 sibly be derived from the fertilizing element (sper- 

 matozoid). The nucleus then begins series of changes, 

 about which most observers are agreed, but for the 

 details of which the reader is referred to the sources 

 named in the footnote. 



* Organologische Studien. Breslau, 1873-4. 



t TJeber Zellbildung und Zelltheiluiig, Jena, 1875. 



J Beitrage zur Kenntniss der Bildung, Befruchtung, und Thei- 

 lung des thiereschen Eies, Morpholog. Jahrbuch, 1, 1875. 



^ La Maturation de I'oeuf, la Pecondation et les Premieres 

 Phases du Developpement Embryonaire des Mammifferes, d'aprds 

 des Eecherches faites ohez le Lapin. Bruxelles, 1875. 



Excellent abstracts of these four papers, by John Priestly, are 

 found in the Quart. Jour, of Microse. Sci., for July, 1878, vol. 

 xvi, new series. In the same number will be found an original 

 paper by Van Beneden, entitled " Contributions to the History of 

 the Germinal Vesicle,. and of the first Embryonic Nucleus," in 

 which he compares the views of Hertwig with his own. 



II Vorlaufige Mittheilung iiber Untersuchungen betreffend die 

 Ersten Entwickelungsvorgange in Befruchteten Ei von Nemato- 

 den und Schnecken, Zeitsch, fiir Wiss. Zoologie, Bd. xxv ; and 

 "Vorlaufige Mittheilung Einiger Eesultate von Studien iiber die 

 Conjugation der Infusorien und die Zelltheilung, Zeitsch. fiir 

 Wiss. Zoologie, Bd. xxv, 1875. 



^ Beitrage zur Geschichte des Keimblasohens im Wirbelthierei, 

 Archiv fiir Mikrosk. Anat., Bd. viii, 1872. 

 ** On the Anatomy and Development of the Eresh-water Hydra. 

 Leipzig, 1872. 

 If Balfour, Developmental History of Blasiiiobranch Fishes, in 

 the Journal of_ Anatomy and Physiology, January, 1876. 



