244 THE PROTOZOA 



sexual activity. The egg is a potential individual as shown by the 

 facts of parthenogenesis, where, without fertilization, the egg develops 

 to form a new individual. The first appearance of this individual 

 goes back to the germ-glands, where it results from the division of an 

 oogonium. Here is the reproductive act proper ; fertilization is only 

 the liberation of an inhibited development through which the poten- 

 tial individual becomes actual. It leads to no increase, but rather to 

 decrease of individuals, since two potential individuals — egg-cell and 

 sperm-cell — join to form one body." 1 



The phrase "liberation of an inhibited development," if applied to 

 the effect of conjugation among the Protozoa, might be translated into 

 Biitschli's "Verjiingung" ('76), or Engelmann's "Reorganization" 

 {'76)1 or Maupas's " Rejeunissement." In no case does word or 

 phrase explain the phenomenon. From all the facts known at the 

 present time, the only conclusion that can be drawn is that conjuga- 

 tion, apparently, is not the cause of reproduction, but as Biitschli, 

 Engelmann, and Minot long since pointed out, in some unknown 

 way provides the energy for continuing the functions of the indi- 

 vidual, including the power of reproducing. 



SPECIAL BIBLIOGRAPHY VII 



Biitschli, 0. — Studien iiber die ersten Entwicklungsvorgange der Eizelle, der Zell- 



theilung und die Conjugation der Infusorien. Abh. d. Senckenb. natnrf. Gesell. 



Frankfurt a. Main, X., pp. 213-452, 1876. 

 Engelmann, Th. W. — Ueber Entwickelung und Fortpflanzung von Infusorien. 



Morphol. Jahrb., pp. 573-635, 1876. 

 Geddes and Thompson. — The Evolution of Sex. London, 1889. 

 Hartog, M. M. — Some Problems of Reproduction, etc. Q. J. M. S., XXXIII., 



pp. 1-81, 1891. 

 Hertwig, R. — Ueber Kerntheilung, Richtungskorperbildung und Befruchtung von 



Actinosphaerium Eich. Abh. d. K. bay. Akad. d. Wiss. Miinchen, 11. Kl 



XIX., 1898. 

 Hertwig, R. — Mit welchem Recht unterscheidet man geschlechtliche und unge 



scblechtliche Fortpflanzung ? Sitz. Ber. d. Ges.f. Morph. u. Physiol. Miinchen. 



II., 1899. 

 Maupas, M. — Le rejeunissement karyogamique chez les cilies. Arch. d. zool.expir 



et gendr., (2) VII., pp. 149-517, 1889. 

 Minot, C. S. — Growth as a Function of Cells. Proc. Bosl. Soc. Nat. Hist., XX., 1879 

 Schaudinn, F. — Ueber den Zeugungkreis von Paramceba Eilhardi. Sitz. Ber. Akad. 



Wiss. Berlin, 1896. 

 Siedlecki, W. — Ueber die geschlechtliche Vermehrung der Monocystis ascidiae 



R. Lan. Btdl. d. VAcad. d. Sci. d. Cracovie, December, 1899. 

 Wilson, E. B. — The Cell in Development and Inheritance. 2d ed. New York, 



1900. 



1 loc. cit., p. 97. 



