EXPERIMENTS WITH FROGS EGGS. 73 



in the late cleavage stages, the amount of desiccation determin- 

 ing the result. Despite the drying of the egg with its accom- 

 panying flattening, the segmentation cavity appeared in it, as 

 sections showed, and while it generally failed to reach the pro- 

 portions characteristic of normal development (except when the 

 paper was too wet), yet that it should develop at all under the 

 adverse conditions of the experiment, demonstrates that its con- 

 tents are produced, in part at least, as a secretion of the sur- 

 rounding cells. A few sections of these eggs are reproduced in 

 Figs. \-\2. 



A section through an egg that had been placed on a dry piece 

 of filter paper at the two-cell stage, and killed some hours later, 

 is shown in Fig. I. A large segmentation cavity is present in 

 the interior although the egg is flattened below from pressure. 



A later stage is shown in Fig. 2. The egg was attached by 

 its white pole. The blastoccel is large and not very different 

 from that of a normal egg. A still later stage of an egg, that 

 was still further compressed (on one side in this case), is shown 

 in Fig. 3. The segmentation cavity is smaller than in the normal 

 blastula of this age. The reduction is probably connected with 

 the great flattening of the egg. Similarly in the next figure, 

 Fig. 4, the segmentation cavity is reduced in size. In the next two 

 figures, Figs. 5 and 6, the segmentation cavity is larger, and as 

 large, in fact, as that of the normal egg. These eggs were but 

 little compressed, and, therefore, developed more nearly in the 

 normal manner. 



The next two figures, Figs. 7 and 8, show a different type of 

 development. The yolk has been so much injured by the drying, 

 that it has failed to segment, yet it is filled with nuclei each sur- 

 rounded by pigment. Both of these eggs were fastened by the 

 lower hemisphere. The tops of the eggs were less injured, and 

 had divided into small cells, that arch over a large segmentation 

 cavity. 



The next egg is very different, Fig. 9. Here, too, the yolk has 

 been killed, but there is present a solid mass of cells imbedded in the 

 yolk. The egg seems to have been attached to one side of the 

 black hemisphere, and the small cells in the interior are due to 

 the shifting of the interior of the egg. The next figure, Fig. 10, 



