TUBAL HISTORY OF UNFERTILIZED EGGS 73 



appropriately concludes that parthenogenetic development 

 never occurs. Her statement that pregnant (or psuedo- 

 pregnant) condition of the 

 animals should favor par- 

 thenogenesis is not neces- 

 sarily correct since activa- 

 tion may require special 

 physiological conditions. In 

 the unmated mouse, how- 

 ever, Charlton (1917) has 

 described identical modes 

 of degeneration in tubal 

 ova with scarcely an ap- 

 proach to normal cleavage, 

 and out of 152 tubal ova 

 in the unmated rat Mann 

 (1924) found only three 

 which appeared to have 

 undergone a belated parthenogenetic development (see 

 Table VIII). In the rabbit (Pincus, 1930) fragmentation 

 occurs rarely; an o\aim of the type shown in Figure 21 is 

 occasionally encountered. 



The fragmenting ova found in the tubes of rats and mice 



Fig. 21. Rabbit ovum recovered 

 from the tubes 411^ hours after ster- 

 ile copulation showing polar fragmen- 

 tation. (From the Proceedings of the 

 Royal Society.) 



TABLE VIII 



The Conditions of Tubal Ova in Various Portions of the Oviduct 

 IN THE Rat. (From Mann, 1924) 



