512 Embryonic History of the Lens in Bdellostoma 
In the blind fishes, however, we have normal cases of degeneration 
of the eye structures which one might expect to at least partially analyze 
with the aid of the experimental results. Eigenmann” has shown in 
Amblyopsis, a blind cave fish, that a lens structure is present in young 
embryos and soon disappears, being entirely absent in old embryos. No 
connection was noted between the appearance and disappearance of the 
lens and the contact of the optic-cup with the ectoderm, although the 
significance of such a relation is only made clear by the experiments. 
In the adult eye of the burrowing lizard, Rhineura of Florida, Eigen- 
mann recorded that the lens was absent in one-half of the eyes studied, 
while the organ was extremely variable in those eyes in which it was 
found. 
Miiller,” in his early description of the Myxinoids, and lately Allen, 
in studying the eye of the adult Bdellostoma noted the absence of a 
lens. Miss Worthington,’ observing the living animals, records them to be 
totally blind. 
Price,” the first to study the embryos of Bdellostoma, found in a 
young stage that a projection of cells from the inner layer of the ectoderm 
extended toward the optic-cup. In older embryos this structure, which 
Price interpreted correctly to be the lens-bud, had disappeared. 
Kupffer” shows a slight thickening of ectoderm in one of his figures 
and designates it a lens-placode; this he states disappears in older 
embryos. In a former paper I” mentioned the disappearance of the 
lens in the embryos of Bdellostoma. It is thus seen that the development 
of this lens has received only passing notice, while in the light of 
experiments the case seems to have gained sufficient importance to war- 
rant a fuller description. 
While studying the development of the brain and special sense organs 
6 Higenmann, C. H., The History of the Eye in Amblyopsis. Proc. Indiana 
Acad, Sci: 1901. 
7 Miller, J., Vergleichende Anatomie der Myxinoiden, der Cyclostomen mit 
durchbohrtem Gaumen. Berlin, 1839. 
8’ Allen, B. M., The Eye of Bdellostoma Stouti. Anat. Anz., XXVI, 1905. 
° Worthington, J., Contributions to Our Knowledge of the Myxinoids. Am. 
Nat., XX XIX, 1905. 
” Price, G. C., Some Points in the Development of a Myxinoid. Verhandl. 
der Anat. Gesellsch., 1896. 
4 Kupffer, C., Zur Kopfentwicklung von Bdellostoma. manor d. 
Gesellsch. f. Morph. u. Physl., Mtinchen, 1900. 
? Stockard, C. R., The Development of the Mouth and Gills in Bdellostoma 
Stouti. Am. Jour. Anat., V, 1906. 
