74 



THE EGGS OF MAMMALS 



finally disappear either through complete disintegration or, 

 what is more hkely, by phagocytosis (Figure 22). They 

 usually disappear before the succeeding ovulation, although 

 Hensen (1869) has described the retention in a blocked tube 

 of about 100 rabbit eggs apparently from several ovulations. 







Fig. 22. Section through a fragmented mouse 

 ovum recovered 81 hours after a sterile mating. 

 Phagocytes (C) absorb the degenerated cytoplas- 

 mic particles (E). (From the Biological Bulletin.) 



The rate of passage of ova in the tubes and the method 

 of transport have been the subject of considerable contro- 

 versy and discussion (see Parker, 1931 and Hartman, 1932&). 

 It is generally acknowledged that the passage through the 

 upper portions of the tubes is relatively rapid (Anderson, 

 1927; Lewis and Wright, 1935) since except shortly after 

 ovulation both unfertilized and fertilized ova are found for 

 the most part in the lower two-thirds of the tube. The 

 method of propulsion of the ova by ciliary and other tubal 

 movements is adequately discussed by both Parker and 

 Hartman and will not be entered into here. 



