EXPERIMENTS WITH FROG'S EGGS. 



T. H. MORGAN. 



The following experiments were carried out in part during the 

 spring of 1905, and in part during the present year. As the 

 headings of the different sections indicate I have brought together 

 the results of experiments of very different kinds, but since they 

 all bear on the same questions it seemed preferable to put the 

 results together in one paper, rather than to scatter them through 

 several. The following topics are discussed : (i) The Devel- 

 opment of the Frog's Egg out of Water, (2) The Increase in 

 the Size of the Egg during the Segmentation Stages, (3) Oblit- 

 eration of the Blastocoel by means of a Centrifugal Force and 

 the Effect on the Subsequent Development, (4) Removal of the 

 Roof of the Blastocoel, (5) Effects of Cold on the Early De- 

 velopment, (6) The Early Development of the Lithium Larvae 

 of the Frog, (7) Effects of Lithium Chlorid and Sodium Chlorid 

 Acting Together, (8) Effects of Lithium Chlorid and Magne- 

 sium Chlorid Acting Together, (9) The Chemical Versus the 

 Osmotic Effects of Salt Solutions. 



THE DEVELOPMENT OF THE FROG'S EGG OUT OF WATER. 



In order to determine whether the segmentation cavity of the 

 frog's egg is simply a water-filled space, left by the cells of the 

 blastula as they separate, or whether the cavity is formed by the 

 active secretion of the surrounding cells, I placed eggs on pieces 

 of filter paper and allowed them to develop out of water. On 

 the first assumption, the blastocoel is filled with water, that, per- 

 colating ^/zew// the cells, passes into the interior. The enlarge- 

 ment of the normal egg during the cleavage period shows that 

 water is really absorbed by the egg, but whether this water sim- 

 ply fills the enlarging segmentation cavity, or whether it enters 

 the cells could only be determined by keeping the eggs out of 

 water during the early development. 



In the first experiment the eggs were placed on pieces of wet 

 filter paper after their outer membranes had been removed. The 



