FACTS AND FINDINGS 37 



vidual in which they originally grew, done by Ross G. 

 Harrison and Alexis Carrel. These men were able to take 

 individual cells and groups of cells and keep them alive, 

 in apparently good health, quite outside of their usual 

 habitat. 



The work on the possibility of artificial parthenogen- 

 esis by Yves Delage and Jacques Loeb also belongs in 

 this field. A mere pricking of the frog's egg with the point 

 of a glass or platinum needle, and then washing the egg 

 in blood, will produce fatherless frogs. In other cases, a 

 chemical or physical change of the water in which the 

 eggs are placed will cause unfertile eggs to develop. 



Baltzer's work with the green worm of the Mediter- 

 ranean and the North Seas seems to show that sex may 

 be determined by either environment or food, or a com- 

 bination of both, for he was able to produce intermediate 

 sexes by merely shaking from their usual position, those 

 which would ordinarily have become males, and forcing 

 them to grow in a foreign medium. 



The work of H. S. Jennings on the behavior of the 

 lower organisms seems to demonstrate some ''purposive 

 behavior" even in animals of a very low level. Such ex- 

 perimental work as having a brainless starfish attack and 

 conquer an equally brainless, but none the less formid- 

 able, sea urchin may throw much light on some future 

 experimental psychology. 



Closely akin to this type of experimentation is that of 

 the various "tropisms" — the name given to those ''en- 

 grained constitutional obligations to adjust the body so 



