PAR THENOGENESIS 



mum exposure, they cleave regularly, later becoming larvae 

 which swim at the surface of the sea-water. This method 

 is far simpler than the butyric acid plus hypertonic sea- 

 water method; and in my experience it is also superior. 

 Batallion and Batallion and Tchou working with several 

 species of sea-urchins have confirmed my findings.^ 



Thus, the method of double treatment is unnecessary for 

 sea-urchins' eggs. They, like all other animal eggs so far 

 studied, respond to treatment with a single agent as the 

 author of the method of the double treatment himself has 

 shown in his original studies on three species of sea-urchins. 



The fact that treatment with a single means initiates 

 development of unfertilized eggs renders less difficult the 

 approach toward an understanding of naturally occurring 

 parthenogenesis. 



Every organism, unicellular or multicellular, lives in and 

 depends upon a world of its own. Whilst some have all 

 the oceans, all the earth, as home, or freely roam all the 

 sky, most dwell in a more circumscribed sphere; yet all 

 sense quickly changes in the environment that hems them 

 in. As with individuals, so with the cells in multicellular 

 organisms — to changes in alkalinity, acidity, salinity and 

 temperature they are acutely sensitive. Within only nar- 

 row ranges of alkalinity, acid-, salt-content and temperature 

 can the cells of the human body, for example, exist.- Vary 

 any one of these factors beyond a certain limit and human 

 life becomes impossible, as we all know. The grand wonder 

 of the human body is the maintenance of these factors as 

 constant. 



separation. This finding is true for all the marine eggs named. 

 The inducing of development in the frog's egg by puncture seems to 

 be an exception. 



1 Batallion, 1926; Batallion and Tchou, igsS. See also these 

 workers {/Qjf) on Bombyx eggs. 



- See Barcroft, /pj2; and earlier., CI. Bernard. 



225 



