Proceedings of the Association of American Anatomists XI H 



somatopleiire. The forward branch becomes the anterior cardinal vein; 

 the posterior branch, incorporating in its progress prolongations of the 

 intersegmental arteries, becomes the umbilical vein. The nmbilical vem 

 sends branches toward the aorta, into the posterior limb and less dis- 

 tinctly into the anterior limb. A longitudinal anastomosis of these ves- 

 sels uniting with a sprout from the venous end of the heart, produces the 

 posterior cardinal vein, which then is cut ofE from the umbilical vem, 

 carrying with it the veins from the limbs. The transverse vems extend 

 from near the duct of Cuvier to the ventral side of the visceral arches, 

 forming a transverse anastomosis. They are found as early m develop- 

 ment as the posterior cardinal veins. The superior mesenteric vem 

 develops as a new branch and is not a persistent vitelline vein. The 

 vitelline arteries exist before the segments form and are not segmental 

 structures. The irregular, small arteries around the fourth entodermal 

 pouch do not, as Zimmerman believed, form a distinct aortic arch. 



EXPERIMENTAL STUDIES ON THE DEVELOPMENT OF THE EYE IN 

 AMPHIBIA. By Warren H. Lewis. Department of Anatomy, Johns 

 Hopkins University. 

 Spemann's experiments on triton, which were performed by punctur- 

 ino- the eye-spot before closure of the medullary folds, indicate that the 

 lens is dependent on the influence of the optic vesicle on the skm for 

 its origin. For if the eye is destroyed, the lens fails to develop, but if it 

 regenerates and touches the ectoderm a lens is formed, while if it regen- 

 erates and remains deeply buried no lens forms. Such deeply buried 

 optic vesicles may invaginate and the optic cup form without the presence 

 of the lens. Without the eye, the clearing of the epithelium for the cor- 

 nea is absent. . 



To test these and other points, I employed, during the spring ot IJOd, 

 a quite different series of experiments. By use of the binocular micro- 

 scope one can make minute dissections of the living amphibian embryo 

 and can remove various organs, transplant them or alter the normal 

 relations, and so alter the influences they exert on each other. We may 

 thus determine certain correlations necessary to normal development. 



The first series of experiments was to turn forward a skin flap from 

 over the optic vesicle of Eana palustris and then to remove the optic 

 vesicle. These operations, as also those in most of the other series, were 

 done before any trace of lens formation was present, that is, shortly after 

 closure of the neural folds. When the optic vesicle failed to regenerate, 

 the lens was absent. If the eye regenerates sufaciently to come in con- 

 tact with the skin a lens will form. If the regenerated eye is deeply 

 buried, it may invaginate, but a lens does not form. 



