58 ILLINOIS ACADEMY OF SCIENCE 



that sex may in some cases be determined by the water con- 

 tent of the egg colloids at the time of fertilization. Eggs of 

 frogs fertilized when laid give about half and half male and 

 female. If they soak in the watery fluids of the oviduct of the 

 female for some hours or days before fertilization they give 

 predominently (sometimes 100 per cent) males. If toad eggs 

 are fertilized as soon as laid they produce about half males and 

 half females, but if dessicated before fertilization females 

 dominated, in some experiments 9 to 1. In hybrids between 

 certain pigeons Riddle finds high water content of the yolk 

 generally correlated with maleness and low water content 

 with femaleness (22). 



On the plant side also there are results that may be inter- 

 preted as meaning that water content of cell colloids of vari- 

 ous primordia have a prominent part in determining the course 

 of development of those primordia. According to MacCallum 

 (23) the markedly different type of leaves in Proserpinaca 

 palustris developing in water and air is due to differences in 

 water contents and Klebs (7: p. 488) finds that in flowering 

 plants high water and salt supply (especially nitrates) leads to 

 vegetative growth, while low water and salt (especially ni- 

 trates) along with high carbohydrates induced reproduction. 

 The nitrates here belonging as they do to the least hydrated 

 end of the lyotropic anion series may act similarly to greatly 

 increased water supply by inducing greater hydration of the 

 cell colloids 1 . 



From these illustrations the question naturally arises : Why 

 does the degree of hydration, or water imbibition, by the pro- 

 toplasm play such an important role in the course of develop- 

 ment of the primordia? The question is not capable of answer 

 at present. It should be pointed out, however, that many other 

 physical characters (viscosity, degree of dispersion, etc.) of 

 the colloidal mass vary correlatively with water supply 2 . 



In the mammal nervous control and internal secretions, act- 

 ing perhaps through correlations, are two very important mor- 

 phogenic determiners. If the degree of hydration of colloids 

 turns out to be as significant as the illustrations above indicate 

 we have here a point of great interest. 



Schroeder (2 : p. 42) has pointed out a character of colloids 

 that has much of interest to the plant physiologists. He finds 

 that a gelatin gel is in equilibrium with a saturated atmosphere 

 when it contains about 40 per cent of its dry weight in water 



1. This interpretation is quite different from that given by Klebs. 



2. Here some will contend that turgor pressure rather than hydration of col- 

 loids is the determining condition. 



