176 Charles R. Stockard 



as shown below that Fundulus embryos develop in a ^ m solution of 

 MgClj in sea-water. Here we have a pressure of about thirteen 

 atmospheres above that of sea-water, while as indicated above a 

 pressure of twelve atmospheres more than sea-water is fatal within 

 twenty-four hours when exerted by a cane sugar solution. A pos- 

 sible explanation of such results is that some of the cane sugar 

 becomes inverted and, therefore, exerts a pressure greater than 

 that estimated, since two molecules are now present for each one 

 calculated. The difference in activity which Jenkinson ('06) has 

 lately recorded between isotonic solutions of cane sugar and dex- 

 trose on the frog's egg may also be due to the cane sugar having 

 become partially inverted and, therefore, his solutions may not 

 have been isotonic, as he thought; at least this explanation seems 

 just as probable as the one he advances, that the membranes dif- 

 fer in their permeability to the two sugars.^ 



The augmentation of the effect when salts are added to sugar 

 solutions that Morgan ('06) has recorded for the frog and as I shall 

 show below for the fish egg may be largely due to the increased 

 pressure or to the peculiar injurious effect caused by some action 

 of the cane sugar. The sugar used in most of my experiments was 

 crystallized "rock-candv, " and was probably pure. 



In those solutions of sugar which exert a pressure lower than 

 that of the sea-water the embryos develop normally and often at 

 a rate faster than that of the control. This acceleration probably 

 is due to their floating and hence being better aerated. Another 

 point of interest regarding eggs in these solutions is that the yolks 

 often become sivoUen as ivould be expected in hypotonic solutions. 

 This observation has never been recorded for these eggs in fresh 

 water nor in any distilled water salt-solutions which were hypo- 

 tonic to sea water. I have treated them with numbers of such 

 solutions, always making careful study of the structural or form 

 changes which resulted, but in no case have I observed a swelling 

 of the yolk except in some, not all, of these hypotonic sugar solu- 

 tions. This swelling may be due to the sugar becoming inverted 



^ This spring I have had an opportunity to compare the action of cane sugar with simple sugars, such 

 as glucose andlevulose, on the frog's egg, and find that the effects of the cane sugar can be explained 

 without assuming any inversion to take place. 



