No. 526] SEXUAL REPRODUCTION IN ANGIOSPERMS 621 



from the union of an enucleated egg-fragment of the 

 sea-urchin and the sperm of a crinoid, could have de- 

 veloped into an adult, or even into the larval stage, 

 which still revealed only maternal characters, the cyto- 

 plasm might have regained some of its old-time prestige, 

 but even then it is doubtful whether that fact would have 

 wrested from the nucleus its monopoly as a transmitter 

 of parental characters. 



In such cases as the embryo hybrid of sea-urchin and 

 starfish, mentioned in the foregoing paragraph, it seems 

 very probable indeed that the cytoplasm of the egg di- 

 rects and even controls the growth of the embryo for 

 a short time subsequent to fecundation, but it is very 

 improbable that the cytoplasm does more. Even in the 

 case of a complete fusion of the egg and sperm nuclei, 

 this and similar experiments seem to indicate ' only the 

 dominance of the egg nucleus over that of the strange 

 sperm. "With the egg nucleus operating in its own 

 special environment, and attributing a directive or regu- 

 lative function to the cytoplasm, the result is what might 

 reasonably be expected. That the cytoplasm is differ- 

 entiated, and that it directs or regulates the formation 

 of certain parts of the embryo in some animals, is clearly 

 shown by the various interesting and important studies 

 of cell lineage carried out by Conklin ( '05 ) and others. 

 Important and far-reaching as are these studies in con- 

 tributing to our knowledge of living protoplasm, they 

 do not teach us very much concerning the cytoplasm as 

 an heredity bearer, nor do I understand that the respec- 

 tive observers make such claims. 



The stimulation of egg-cells to growth and division by 

 immersing them in water having different physical or 

 chemical properties than their normal surroundings, or 

 by injecting chemicals into the ovaries or ovules by 

 means of an hypodermic syringe, are lines of study that 

 are valuable and interesting in showing the response of 

 living cells and tissues to external stimuli, for it is the 

 business of the physiologist to know what cells can do 

 under any and all conditions ; but that these experiments 



