Independent Development of the Lens. 423 
EXPLANATION OF PLaTEs I anp II 
Fig. 1 A photograph of a section of a seventy-six hour Fundulus embryo; the 
brain is almost bilateral and perfect, with a well formed left optic cup, no indica- 
tion of the right cup exists, yet the ectoderm on that side has formed a well 
pronounced lens-bud, L. 
Fig. 2 A section through the eye region of a thirty day embryo, there is no 
optic cup in the specimen. A perfect lens is in the usual lateral position, L, a 
band of muscle, M, lies between it and the brain. 
Fic. 3 A section through the head of a Fundulus embryo eighteen days old. 
The specimen is shown in text-figure 1, no eyes are present, yet two perfectly differ- 
entiated crystalline lenses are seen in the sides of the head. A close examination 
of the photograph will reveal mesodermal cells between the lens and the brain. 
Fig. 4. A section through one defective eye which possesses a lens of dispro- 
portionate size, while on the other side of the head two free lenses are seen, the 
lower small one protruding from the head. A second defective eye with a lens 
is found in a more posterior region of the head. Text-figure 4 represents this 
embryo as it appeared in life. 
Fic. 5 A section through one of the very defective optic vesicles shown in 
fig. 2. The photograph illustrates the extreme lack of proportion which may 
exist between the size of the optic vesicle and its associated lens. It indicates 
also how small an amount of optic tissue may stimulate lens formation from the 
ectoderm. 
