EARLY DEVELOPMENT IN THE FROG. 337 



Experiments IV 70; G, H, I. Eggs deposited March 28, 

 3:00 P.M. Removed to the laboratory 4:00 P.M. Introduced 

 into m/ 500,000 HgCU, 5:00 P.M. unsegmented at this time. 

 After 24 hours the eggs were washed and returned to water. 

 Twenty-four hours later (March 29, 5:00 P.M.) the stages 

 shown in Fig. 14 were recorded. About 40 per cent, of the eggs 

 showed the V-shaped blastopore (Fig. 14, A). Eggs in the three 

 experiments were alike and among them everything was present 

 from a few with closed blastopores to several forms showing a 

 secondary invagination midway between the original (equatorial) 

 blastopore and the apical pole. The equatorial gastrulse resemble 

 those produced in m/io LiCl. 



Experiment IV 91. Unsegmented eggs, placed in w/2,ooo,ooo 

 HgClo. Forty hours later, the eggs were mostly in inhibited gas- 

 trula stages (V-shaped blastopores). 



Eggs introduced into m/ 10.62 LiCl during 16-32 cell stage, 

 exhibit the inverted V- or U-shaped blastopore after 24 hours' 

 exposure (Experiment IV 76). Eggs introduced into m/io LiCl 

 immediately before gastrulation (Experiment IV 59) are in 

 gastrula and large yolk plug stages after eighteen hours in the 

 solution. The majority of gastrula stages show the long in- 

 verted V-shaped blastopore and in those eggs showing yolk plugs, 

 there is a tendency for the yolk plugs to be much larger than 

 normal and somewhat oval in shape (Fig. 16). 



After 48 hours in the solution, ninety per cent, of the eggs 

 were in early neural fold stages, with much elongated yolk plugs. 



In experiment IV 62 unsegmented eggs, five hours after deposi- 

 tion, were introduced into 0.0075 per cent, formaldehyde, and 

 varied from equatorial gastrulae to early neural fold stages after 

 sixty hours' exposure. A few showed secondary invaginations. 



In experiment R 138 a, eggs in early gastrula stages were 

 placed in m/i,ooo KNC. After a 12-hour exposure, 90 per cent, 

 of the eggs showed a long inverted V-shaped blastopore or much 

 elongated yolk plug. The eggs did not develop farther in this 

 solution. 



(b) and (c) Retardation of Both Dorsal and Lateral Lips of the 

 Blastopore, and Equatorial Gastrulation. Eggs showing retarda- 

 tion of both dorsal and lateral lips are described as " flat-crescent" 



