190 
and crowded the optic vesicle outside its cavity but the eye remained 
reversed. A lens lies in the cavity of the secondary optic vesicle, and 
it was evidently formed from the anlage of the nasal organ of the same 
side. The nasal anlage having been drawn aside by the optic vesicle 
does not reach the pharyngeal region. Normally it is connected to 
the pharynx long before this stage. From the ectodermal origin of the 
nasal anlage a thin cord of epithelium goes to the pharynx connecting 
with it in the normal position. 
Embryo 363, 3,2 mm long. The right optic vesicle was dissected 
out and put in the cavity of the brain through an opening in the mid- 
dorsal line. Its ventricular attachment was directed dorsally. It was 
killed the fifth day after the operation. The secondary optic vesicle 
lies almost entirely inside the brain cavity but one margin projects 
through the roof. A regenerated eye has grown into the brain from 
below and fused with the transplanted eye through part of its lower 
surface so that the cavities of the two eyes are in close communication. 
A lens was formed from the ectoderm above as shown by the long 
cord which still persists and connects it. The lens extends through 
the entire brain going to both eyes and finally passing out below and 
terminating in the connective tissue above the pharynx. 
Embryo 344, 3 mm long. This embryo was operated as 345, and 
killed the fifth day after the operation. The result is difficult to inter- 
pret. A complex eye with two large lenses lies in the normal position 
of the eye, and a small retina projects well into the brain cavity. One 
of the lenses outside passes into the brain and forms the lens of the 
intracranial eye. Only the extremities of this long lens, i. e. the parts 
in the cavities of the two eyes, are differentiated into lens fibres. 
In a number of embryos the lens was developed from the margin 
of the secondary optic vesicle. 
In no case is a structure positively identified as a lens unless 
the typical lens fibres and epithelium are present. 
A number of experiments were made in which the optic vesicle 
was placed against the endoderm of the pharyngeal region of the 
alimentary canal, but in no case was any sign of lens formation from 
the endoderm observed. 
W. H. Lewis has shown that the lens may be developed from 
the ectoderm of the same side of the body back of the eye- region; 
Wo trr, that the lens may be regenerated from the iris; and FISCHEL, 
that lentoids may be developed in the retina proper (the inner layer 
of the secondary optic vesicle) after removal of the lens. My results 
show that a typical lens (with lens fibres and epithelium) may also be 
— TE 
