THE INFLUENCE OF EXTERNAL FACTORS, CHEM- 

 ICAL AND PHYSICAL, ON THE DEVELOPMENT 

 OF 'FUNDULUS HETEROCLITUS 



BY 



CHARLES R. STOCKARD 



With Seventeen Figures 



The following experiments have been undertaken to determine 

 to what extent the form of the embryo and its manner of develop- 

 ment might be modified by external influences. In a previous 

 paper ('06), I have shown that lithium chlorid produces a definite 

 effect on the development of Fundulus heteroclitus, as Herbst 

 ('92) had shown for the sea-urchin and Morgan ('03) for the frog. 

 During the past summer I have been able to show that these 

 abnormalities are not only definite but specific for the lithium ion 

 in its action on this egg. 



It has also become desirable, owing to recent work on the sub- 

 ject, to determine the permeability of the membrane of Fundulus 

 eggs to the various salts; as well as to study the separate and com- 

 bined effects of osmotic pressure and chemical actions on the 

 development. The eggs of Fundulus, as has often been recorded, 

 develop almost equally as well in sea-water, concentrated sea- 

 water, fresh or distilled water, and even, as Morgan ('06) has 

 re ently mentioned, out of water. ' Thus they furnish excellent 

 material for a study of the actions of both hypertonic and hypo- 

 tonic solutions. 



The experiments were performed at Wood's Hole, Mass., while 

 occupying a table kindly furnished me by the Vassar Brothers' 



' In regard to the development of these eggs in fresh water. Loeb ('94) states: "In fresh water the 

 embryos hatch just as rapidly as in normal sea-water. The fish is able to live in fresh water.'' On 

 the contrary, I have shown (Stockard, '06), that these eggs are always slower to hatch in fresh water and 

 further that the newly hatched young soon die when left in this medium. Sumner ('06) has also shewn 

 that the adult fish is unable to survive in perfectly fresh water. 



The Journal of Experimental Zcology, vol. iv, no. 2. 



