FUSION OF UPIBLASTIO LAYERS IN RABBIT AND FROG. 171 



DESCRIPTION OF PLATE 18, 



Illustrating Mr. Richard Assheton's paper, *' On the Phe- 

 nomeuon of the Fusion of the Epiblastic Layers in the 

 Rabbit and in the Frog." 



List of Reference Letters. 



All. Auditory vesicle. E. NE. Nervous epiblast. E. EP. Epidermic 

 epiblast. NE. Neuroblast. PL Stalk of pineal gland. PB. Processes of 

 epidermic layer cell. T. E, Band of nerve-fibres passing from ganglion 

 habenula to the ventral side of the brain. 



Fig. 1. — Transverse section through a portion of the neural plate of a frog 

 embryo (Rana temporaria) during the process of folding up of the neural 

 plate. Unstained. X 165. 



Fig. 2. — Transverse section through corresponding region, but at a slightly 

 later period, of a frog's embryo. Unstained. X 165. 



Fig. 3. — Transverse section through the corresponding region after the 

 separation of the neural tube from the skin. Tadpole, 3| mm. Unstained. 

 X 165. 



Fig. 4. — Transverse section through the spinal cord of the same specimen 

 as Fig. 3. Unstained, x 165. 



Fig. 5. — Transverse section through ganglion habenula of a frog tadpole 

 of 13 mm., showing deeply pigmented neuroblastic processes. Aniline blue- 

 black, x 350. 



