IO6 H. H. NEWMAN. 



IV. SCOPE AND OUTLINE OF OBSERVATIONS. 



The present study begins with a consideration of conditions 

 found in ovocytes at the beginning of the period of growth, just 

 before they have acquired primordial follicles. It appears 

 necessary to begin the study of maturation thus early partly 

 because the prophases of maturation appear to be well under 

 way at this period and partly because the development of the 

 follicle and the relations of the ovocytes to the follicle are of 

 fundamental interest in connection with the investigation into 

 the causes of polyembryony. The growth of the ovocyte is 

 accompanied by growth and modification of the follicle and the 

 development of both culminates in a condition which would 

 normally be followed by ovulation. Failure of ovulation, how- 

 ever, is the fate of the vast majority of developing ova, owing 

 partly to their position in the ovary but chiefly to the influence 

 of pregnancy, the occurrence of w r hich inhibits further ovulation. 

 These ova which have reached full size and are in every way 

 mature and ready for ovulacion, occasionally complete the 

 process of maturation in a manner identical with that which 

 normally occurs only in ova which have been fertilized, and under 

 some conditions develop parthenogenetically through the cleav- 

 age period, as I have determined quite conclusively. In lieu of 

 any data concerning the completion of the second maturation 

 division in tube eggs, it is considered a legitimate procedure to 

 substitute an account of the condition seen in these ovarian ova 

 in which the maturation process has proceeded beyond the 

 stage ordinarily seen in such ova. That this is a justifiable use 

 of mateiial is shown by the fact that in all species where both the 

 normal process of maturation, and that seen under conditions 

 identical with those just indicated, have been studied, there 

 has been found no essential difference between them. 



The study then may be conveniently divided into two parts, 

 the first dealing with processes taking place in normal follicles 

 up to a period when ovulation would normally take place, and 

 the second with the completion of the maturation in follicles 

 undergoing the early stages of follicular atresia. In all other 

 species where the facts are known ovulation occurs during the 



