THE EGGS OF MAMMALS 



CHAPTER I 

 INTRODUCTION 



The behavior of mammahan eggs from the time of their 

 genesis in the ovary to their implantation in the uterus is 

 the subject matter of this book. The attempt has been made 

 to include experimental investigations of the growth and 

 development of ova rather than morphological descriptions. 

 This is not an easy task, because an acute morphologist 

 may make deductions about the nature of his material 

 which are far more illuminating than those of an eager but 

 inexpert experimenter. Furthermore, except for certain 

 notable investigations of ovarian dynamics, there has been 

 no extensive inquiry into the physiology of living mam- 

 malian ova. It has been tacitly assumed, for example, that 

 the reactions involved in the activation of non-mammalian 

 ova occur also in mammalian eggs. Until quite recently no 

 attempt has been made to test even this assumption. Since 

 the middle of the last century a controversy has raged 

 about the possibility of ovarian parthenogenesis. Almost 

 every observer of mammalian ovaries has contributed an 

 opinion, but no one has tried to see if ovarian eggs can be 

 induced to develop parthenogenetically. Experimentation 

 has lagged presumably because of the difficulty of handling 

 living ova. 



It is interesting to note that the discovery of the mamima- 

 lian egg by von Baer in 1827 led initially to extensive ob- 

 servations of living ova. At first the exact morphology of 

 the egg and its membranes was a matter of some debate 

 (see Wagner, 1836; Jones, 1837, 1838, 1885; Barry, 1838; 



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