132 THE PHYSIOLOGY OF REPRODUCTION 



shown already, 1 the polar bodies are formed while the ovum 

 is still in the ovary, but not until after the occurrence of 

 copulation. 



In the case of the mouse, Sobotta 2 came to the conclusion that 

 the first polar spindle is suppressed, and that the second polar 

 body might be formed during the passage of the ovum down 

 the Fallopian tube. Gerlach 3 describes the second polar body 

 as being in some instances suppressed after the entry of the 

 spermatozoon in fertilisation, the second polar spindle degenerat- 

 ing within the egg. Kirkham, 4 however, states that the matura- 

 tion of the mouse's ovum is in no way exceptional, the process 

 involving the formation of two polar bodies as in most other 

 animals. The first polar body is extruded in the ovary, while 

 the second is given off in the Fallopian tube immediately after 

 fertilisation by a spermatozoon. 5 Rubaschkin 6 has shown that 

 the maturation processes in the guinea-pig are similar. In both 

 the guinea-pig and the mouse, ova which are retained in the 

 ovary, and also those which are discharged and fail to become 

 fertilised, undergo degeneration with the second polar spindle 

 within them. 



The maturation phenomena in the bat (Vesperugo noctula) 

 have been investigated by van der Stricht, who has published a 



1 Heape, loc. cit. 



2 Sobotta, " Die Befruchtung und Furchung des Eies der Maus," Arch, 

 f. Mikr. Anat., vol. xlv., J895. 



3 Gerlach, Ueber die Bildung der Richtungskorper bei Mus musculus, 

 Wiesbaden, 1906. 



4 Kirkham, "The Maturation of the Mouse Egg," Biol. Bull., vol. xii., 

 1907 ; and " The Maturation of the Egg of the White Mouse," Trans. Con- 

 necticut Acad. Arts and Sciences, vol. xiii., 1907. 



5 Sobotta ("Die Bildung der Richtungskorper bei der Maus," Anat. Hefte, 

 vol. xxxv., 1907), in a further paper, expresses himself doubtful as to whether 

 two polar bodies are really discharged in all cases in the maturation process 

 of the mouse's ovum. His own observations lead him to conclude that two 

 polar bodies are discharged in not more than one-fifth of the total number 

 of maturations, only one polar body being formed in the great majority 

 of cases. Lams and Doorme (" Nouvelles Recherches sur la Maturation et la 

 Fecondation de 1'CEuf des Mammifcres," Arch, de Biol., vol. xxiii., 1907) 

 state that they found two polar bodies expelled in forty -four cases out of 

 forty-eight, the first being always smaller than the second. 



6 Rubaschkin, " Ueber die Reifungs- und Befruchtungsprocesse des 

 Meerschweincheneies," Anat. Hefte, vol. xxix., 1905. 



