The Influence of External Factors oii Development 179 



other hand sea-water is neutral and the sugar would be much less 

 disposed to invert under such a condition. A fungus-like growth 

 often attacks eggs in fresh water, while I have never observed any 

 such growth about eggs that were immersed in sea-water. The 

 fungus grows in a slightly acid medium and is often present in 

 fresh water solutions of sugar. The acid condition of a solution 

 is in itself injurious. Owing to these conditions a frequent change 

 of the sugar solutions was necessary. 



Solutions of glucose and glycerine were also used to test osmotic 

 effects but these chemicals proved to be impure. 



THE SPECIFIC CHARACTER OF THE LITHIUM EMBRYO 



In my paper on the devlopment of Fundulus in solutions of LiCl, 

 it was only possible to state at that time that lithium induced certain 

 definite effects which were characteristic of this salt's action. It 

 was also suggested that these effects might be specific for lithium 

 but such could only be known after a number of other lithium 

 salts, as well as a numberof the salts of other metals had been used. 

 I have since employed many other metalhc salts and have found 

 none of them to produce with any constancy the abnormalities in 

 development which result from the use of lithium salts.^ 



An experiment was first carried out in which eggs were subjected 

 to solutions of LiNOg and LijSOg to ascertain whether the resulting 

 development would be similar to that found in LiCl solutions. 



Eggs were placed soon after fertilization in distilled water solu- 

 tions of LiNOg i m and sV m, and LijSO^ tV m and 5V rn. The 

 first four or five hours of development was almost normal, but 

 after eight hours those in LiNOg 2V rn were beginning to send a 

 projection of the periblast down into the yolk substance, a contin- 

 uation of this process results in the large bubble-like segmentation 

 cavity before described ('06). When twenty-two hours old the 

 germ-ring is just below the equator in the control (Fig. 9). Those 



^ Madame Rondeau-Luzeau ('02) and Morgan ('06) have found that the upper limit of LiCl that the 

 frog embryo can stand is a 0.65 per cent solution, the osmotic pressure of which is 5. 161 atmospheres, 

 while the upper limit of NaCl is about 2 per cent and exerts a pressure of 13.61 atmospheres which 

 is more than double that of the lithium solution. This comparison shows that the effects of the lithium 

 salt are not due to its osmotic pressure alone. 



