XXXIII 



EXPERIMENTS ON ARTIFICIAL PARTHENOGENESIS IN 

 ANNELIDS (CH.ETOPTERUS) AND THE NATURE OF 

 THE PROCESS OF FERTILIZATION 1 



I. INTRODUCTION AND METHODS 



MY preceding papers on artificial parthenogenesis 2 had 

 proved that by an increase in the osmotic pressure of the 

 sea-water the eggs of many, if not all, Echinoderms can be 

 caused to develop parthenogenetically. Two new problems 

 presented themselves for immediate consideration. The one 

 was to raise the parthenogenetic Iarva3 until they were sex- 

 ually differentiated, in order to decide whether or not they 

 are of uniform sex. The second problem was to try whether 

 artificial parthenogenesis is confined to the group of Echino- 

 derms or whether it is a more general phenomenon. As the 

 means for the raising of sea-urchins were not available at 

 Woods Hole this year, the former problem had to be post- 

 poned. The solution of the second problem, however, was 

 possible, and yielded the result that the unfertilized eggs of 

 Chsetopterus, a marine Annelid, can be caused to develop into 

 swimming ciliated Iarva3 (trochophores). A short preliminary 

 report of this result has been published in Science. 3 



In experiments on parthenogenesis the greatest precau- 

 tions are necessary to exclude the possibility of a contamina- 

 tion of the eggs by spermatozoa. I purposely selected 

 Chffitopterus for my further experiments on account of the 

 possibility of discriminating between and separating the 

 females and males. If the experimenter handles females 

 and males in the same experiment or with the same instru- 



1 American Journal of Physiology, Vol. IV (1901), p. 423. 



2 Part II, pp. 539, 576, 624, and 638. 3 Science, Vol. XII (1900), p. 170. 



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