Embryonic Germ-Cells. xxvii 



sidered that the function of forming polar cells had 

 been acquired by the ovum for the express purpose of 

 preventing parthenogenesis. Van Beneden ^ and Minot - 

 regard the polar bodies as male elements removed from 

 a hermaphrodite cell. Biitschli, Hertwig ^, and Boveri 

 incline to regard them as abortive ova and an atavistic 

 reminiscence of primitive parthenogenesis. Geddes and 

 Thomson ^ consider their extrusion due to the tendency 

 of every cell to divide at the limit of growth, but favour 

 the view that the process may be an extrusion of male 

 elements. They consider, however, that these cells have 

 no history, though they occasionally linger on the 

 outskirts of the ovum, are seen to divide, and be 

 penetrated by ' misguided ' spermatozoa ^ 



The homologous character of oozoa and spermatozoa 

 has been pointed out, and these so far retain the habits 

 of their protozoan ancestors as to require conjugation: 

 in the parthenogenetic form, the two oozoa conjugate 

 in each oocyte, in the sexual form one oozoon and 

 one spermatozoon unite to form the fertilized ovum 

 or oosperm, but I believe the three oozoa which 

 form the polar bodies, unite together or conjugate 

 with three spermatozoa, previous to that repeated 

 division by which those bodies are prepared to be 

 received as the earliest embryonic germ or sperm-cells 

 into the rudimentary germ-tracks*'. 



^ E. Van Beneden, ' Recherches sur la fecondation,' Arch, de 

 Biologic, iv, 1883. 



- C. S. Minot, ' Theorie der Genoblasten,' Biol. Ceiitralbl. ii. p. 365. 



3 O. Hertwig, Die Zelle iind die Gcwebe, Jena, 1892. 



* Geddes and Thomson, Evolution of Se.x, p. 107, 1892. 



^ Ibid. p. 105. 



^ H. Henking, Zeitschr. f. wissensch. Zoologie. liv. 89 ; V. Graber, 

 * Keimstreif der Insecten,' Denkschrift d. K. K. Akad., Mafh.-Nat. CI, 

 Wien, Ivii, T890. 



