ARTIFICIAL PARTHENOGENESIS 485 



the acids become, if carbonic acid, H2C0,^ be excepted, which is 

 wholly hypothetical as a member of the group to which the others 

 belong. 



4. Temperature, mechanical agitation (which was not men- 

 tioned) and environmental conditions other than what have 

 been enumerated were not found to be efficient in causing even 

 the expulsion of polar bodies. It was not found possible to note 

 any constant variable between the Harpswell conditions and 

 those at New Haven, although the differences were as great as 

 one could desire for the experiments. 



5. There is reason to believe that a strong cytolyzing reagent, 

 like HCl or saponin, followed by a weaker one, such as CO2 is 

 efficient in carrying out segmentation. However, it was not 

 possible to carry the segmentation by any means beyond the 

 earl}' morula stages. There is clearly here a difference between 

 maturing and segmentation-inducing reagents. 



It will be seen that the experiments to be described upon arti- 

 ficial parthenogenesis plus the action of foreign spermatozoa are 

 not easily confused as to the factor at work, for in all cases where 

 the artificial parthenogenetic reagents were used alone (as in the 

 above experiments) the development progressed only to the 

 early morula stages. Hence, if the spermatozoa of the foreign 

 individual exerted any effect, it would be readily recognized, if 

 the effect were at all worthy of notice, that is, efficient in producing 

 an approach to normal development wherein the segmentation 

 proceeded past the early morula stages. 



As stated in a previous footnote, the polar bodies of Cerebrat- 

 ulus are not expelled until the spermatozoon enters and in this 

 respect, it resembles other animals which have been examined 

 with respect to artificial parthenogenesis, such as the annelid, 

 Polynoe (Lepidonotus) (Loeb '08) ; Chaetopterus (Mead '98) ; 

 Thalassema (Lefevre '07) and others. Compared to them, how- 

 ever, in regard to the reagents which bring about the whole or 

 completion of maturation, there is a great difference as far as my 

 observations are concerned. In regard to Polynoe, Loeb found 

 that ''die Eier von Polynoe konnen aber auch im Seewasser ohne 

 Spermatozoon zur Reifung gebracht werden, wenn man dem See- 



