128 THE PHYSIOLOGY OF REPRODUCTION 



papers on the subject.^ This observer states that there are always 

 two polar bodies formed. The first is extruded in the ovary. The 

 second spindle is formed at about the ovulating stage, and the second 

 polar body is discharged in the interior of the Fallopian tube. The 

 first body is formed in February or March, or sometimes later 

 according to the temperature.^ 



It would seem that in the case of the mole the two polar bodies 

 are discharged while the ovum is still retained within the ovary .^ 



In the pigeon it has been shown that the polar bodies are given 

 off while the ovum is passing down the glandular portion of the 

 oviduct and after the entrance of the spermatozoon. The first polar 

 spindle, however, is formed in the ovarian egg ; but it is not definitely 

 known at what stage fertilisation occurs, excepting that it is previous 

 to the time when the egg is clasped by the oviducal funnel. , 



In the frog the polar bodies are extruded after ovulation has 

 taken place, but the egg is not set free until it has reached a certain 

 stage of maturation, which is preparatory to the discharge of the 

 first polar body. The nucleus undergoes a change, and, in place of 

 being large and watery, consists of a small mass of chroma^tic 

 substance lying in the protoplasm. An achromatic spindle is 

 developed, and the chromatin becomes arranged in the form of 

 granules at the equator of the spindle. The nuclear membrane 

 disappears with the large watery nucleus. The ova in this condition 

 pass into the oviducts.* 



In certain Invertebrates (Nematodes, Annelids, and Gasteropods) 

 it has been noticed that the occurrence of the maturation phenomena 

 depends upon the act of fertilisation. For example, in the Japanese 

 Palolo-worm, a marine Polychaet Annelid, Izuka * has shown that the 



' Van der Stricht, "La Ponte ovarique, etc.," Bull, de I'Acad. Roy. de Mid. 

 de Bdgique, 1901. Une Anomalie tres interessante conoernant le DSveloppement 

 (Sun CEiuf de Mawmdfere, Gand, 1904. " Les Mitoses de Maturation de I'CEuf 

 de Chauve-Souris," Mimoire presentd aii VIII' Gongres de I' Assoc, des Anatomistes, 

 Nancy, 1906. 



2 Van der Strieht says (Za Stmcture de I'CErtf des Mammiferes, Bruxelles, 

 1909) that he has seen twenty-two ova at the stage of the second polar 

 spindle within the ovary and twenty-seven at the same stage outside of the 

 ovary, the dates varying in each case from the end of February to the end 

 of April. See below, p. 183, Fig. 58. 



^ Heape, "The Development of the Mole," §ijar. Jour. Micr. Science, 

 vol. xxvi., 1886. For further information as to maturation phenomena, see 

 von Winiwarter {loc. cit., for man) ; von Winiwarter and Sainmont {Nowvelles 

 recherches sur I'ovogenese, Liege, 1912, for cat) i~Van der Strieht (" Vitelleg6nfese 

 dans I'Ovule de Chatte," Arch, de Biol., vol. xxvi., 1911, for cat) ; and Corner 

 (" Maturation of the Ovum in Swine," ^nai. Record, vol. xiii., lQl'J,ior pig); 

 also Athias, Sobre as Divisoes de Maturacao do Omdo dos Mammiferos, Lisbon, 

 1910. 



* Morgan, Tfie Development of the Frog's Egg, New York, 1897. 



^ Izuka, " Observations on the Japanese Palolo," Jour, of the Coll. of Science, 

 University of Tokyo, vol. xvii., 1903. 



