96 THE EGGS OF MAMMALS 



since they exhibited the cyclosis (cytoplasmic movements) 

 typical of living ova. Similar experiments with iodoacet- 

 amide added to the cultures showed normal cytoplasmic 

 activity of the ova but a limited amount of cleavage. lodo- 

 acetamide presumably combines with the coenzyme con- 

 cerned in the reduction of pyruvic to lactic acid (Meyerhof 

 and Kiesling, 1933) so that the inhibition of both the oxygen- 

 activating system and its presumable substrate system re- 

 sults in the arrest of cleavage. While the exact coupling of 

 the respiratory system with the mitotic mechanism has 

 yet to be delineated these data do demonstrate that the 

 fundamental processes are aUke in manomalian and non- 

 mammahan ova. 



We have seen that rabbit ova may be fertilized and cul- 

 tured in vitro. It is a matter of some importance' to deter- 

 mine whether such ova may give rise to normal rabbits. 

 Accordingly the writer (see Pincus and Enzmann, 1934) 

 undertook the transplantation of such ova into the oviducts 

 of pseudopregnant rabbit does and found that ova fertilized 

 in vitro and also normally fertilized ova kept in culture during 

 the cleavage period apparently resumed normal development 

 after transplantation as evidenced by the production of 

 normal young at term. It is a matter of some interest to 

 note that one set of ova had failed to cleave during 20 hours 

 in culture but nonetheless young were obtained. 



The development of a technique for the transplantation 

 of mammalian ova into the oviducts makes possible the 

 testing of a number of problems of development hitherto 

 inaccessible. As we shall see later (Chapter IX) it is neces- 

 sary that a progestational uterus be available for ensuring 

 differentiation of uterine stages. Thus Biedl, Peters and 

 Hof stater (1922) transplanted rabbit ova into non-pregnant 

 uteri in some 70 experiments and in only one doubtful case 

 were young recovered. Nicholas (19336) transplanted the 

 isolated blastomeres of the 2-cell stage in the rat under the 

 kidney capsule and observed varying degrees of development 

 of the three germ layers and their various derivatives. The 



