CHANGES IN THE OVARY 133 



series of papers on the subject. 1 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 ovulat- 

 ing 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. 2 



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. 3 



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 dis- 

 charge of the first polar body. The nucleus undergoes a change, 

 and, in place of being large and watery, consists of a small mass 

 of chromatic 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. 4 



In certain Invertebrates (Nematodes, Annelids, and Gastero- 

 pods) it has been noticed that the occurrence of the maturation 



1 Van der Stricht, " La Ponte ovarique," &c., Bull, de VAcad. Roy. de Mid. 

 de Belyiquc, 1901. Une Anomalie trh inte'ressante concernant le Developpcment 

 d'un CE'uf de Mammifere, Gand, 1904. "Les Mitoses de Maturation de 1'CEuf 

 de Chauve-Souris," Memoire pr<?scnte au VIII e Congres de VAssoc. des Anato- 

 mistes, Nancy, 190fi. 



2 Van der Stricht says (La Structure de VCEuf 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. 



3 Heape, " The Development of the-Mole," Quar. Jour. Micr. Science,vol. xxvi. 

 1886. 



4 Morgan, The Development of the Frog's Egg, New York, 1897. 



