372 G. HAROLD DREW 



An obvious objection to this theory is that the ciliated epithe- 

 Hum is not produced after the implantation of pieces of ovary that 

 have been killed in any of the ways described, but it must be taken 

 into consideration that in these cases the implantation of the dead 

 ovarian tissue was always accompanied by a more or less intense 

 inflammatory reaction, and so the experiments are scarcely com- 

 parable to those in which portions of the living ovary were used. 

 Also it is probable that the chemical composition of the ovary was 

 altered by the methods of killing. 



If by future experiments, and more extended observations, it 

 can be fully substantiated that similar cytological changes take 

 place in other types, as a reaction to the presence of some definite 

 chemical substance, the fact should have an important bearing 

 on the chemical theories of development, and possibly on the 

 origin of certain abnormal heterotopic growths. 



ABSTRACT OF EXPERIMENTS PERFORMED 



Total number of implantations, including animals that died before exami- 

 nation (about) 9''^0 



Number of animals examined in studying stages up to 20 days 215 



Number of animals in which cysts lined with ciliated epithelium were pro- 

 duced (not including those which died between 20 and 130 days, of which 



it is probable that most produced such cysts) 68 



Experiments on effect of heat on ovary before implantation 42 



Experiments on effect of cold on ovary before implantation 18 



Experiments on effect of chemicals on ovary before implantation 48 



Experiments on effect of degeneration on ovary before implantation 22 



Experiments on implantation of centrifugalised ova 10 



Experiments on implantation of ova in gelatin 10 



Experiments on implantation of foreign bodies 33 



Experiments on implantation of ovaries of other animals 46 



Experiments on implantation of ovary of P. maximus to P. opercularis 12 



Experiments on implantation of ovary of P. opercularis into P. maximus 12 



Experiments on implantation of male gonad ^0 



Experiments on implantation of ovary first treated with sperm 14 



Experiments on implantation of portions of ovary containing no oviduct J 2 



Experiments on implantation of portions of ovary containing oviduct 14 



Experiments on implantation of unripe ovary 20 



