The Frog Book 



Plate LXV 



Sid 



e view 



lolk 



-Yolk 



Fig. 202.— April 9, 1902. LEOPARD FROG'S EGG, greatly magnified. The upper portion is black; the lower in 

 cream-white. The first vertical partition is forming. [Providence, R. 1.] 



Fig. 203. — Drawn to show first two vertical grooves corresponding to two partitions which divide the egg into four 

 cells. (Egg tipped to show top.) 



B 



^'Neural 



Qpoove 



Fig. 205. — The cells are too small to be seen. A dark line of crescent shape appears on one side of the egg. 



Fig. 206, A. — Morning of third day (April nth). Egg drawn from posterior end. All of the yolk except a mere 

 plug is covered by the dark living portion of the egg. 



B.— Afternoon of the third day. Egg as seen from left side. Volk-plug marks posterior end of embryo. Neural 

 groove forming along the back. 



Neural fold 



,Neural oroovc 



.^ 



Fig 207.— April 12th. Drawn from left side (as B, Fig. 206) but tipped to show back. The neural folds are closing \ 

 in over the neural groove to form the nerve tube The anterior of this will make the brain, the remainder will be the 

 spinal cord. 



