. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Heteropygii. 140 BLIND VERTEBRATES AND THEIR EYES. geneous, vesicular, ellipsoidal nucleus situated near the outer end of the cell. This nucleus is strikingly different in shape and constitution from the same structure in Chologaster. It stains but faintly and then homogeneously. Just within the nucleus there is. a well-defined mass of dense pigment forming a cap over the inner side of the nucleus and at times encroaching on the rotundity of its inner outline. This pigment mass evidently has its counterpart in Chol
. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Heteropygii. 140 BLIND VERTEBRATES AND THEIR EYES. geneous, vesicular, ellipsoidal nucleus situated near the outer end of the cell. This nucleus is strikingly different in shape and constitution from the same structure in Chologaster. It stains but faintly and then homogeneously. Just within the nucleus there is. a well-defined mass of dense pigment forming a cap over the inner side of the nucleus and at times encroaching on the rotundity of its inner outline. This pigment mass evidently has its counterpart in Chologaster where a solid band of pigment is found just within the nucleus. In depigmented cells this pigment cap is seen as a deeper-staining, more dense protoplasm than the rest of the cell. From this pigment segment a prolongation, much poorer in pigment and containing a central uniformly staining core, extends toward the interior of the eye. This core, which in reality extends also into the pigmented section, occupies the position of the cones in Chologaster. In no case have I been able to trace any connection between these bodies and the outer nuclear layer. They are sometimes in several esgments or in a number of spherical bodies, and occasionally two are seen side by side in the same cell in tangential section. In position they certainly suggest cones,. Fig. 52. Section near Posterior Face of Left Eye of Small Individual, showing particularly Position of one of Scleral Cartilages behind Eye and Thick Choroid filled with more or less Angular Mass of Granular Pigment. This Eye shows one of the Largest Accumulations of Pigment noticed. and this suggestion is heightened by the presence in the inner end of some of the cells of a vesicular structure very similar to the nucleus, but frequently with an angular indentation on the surface. These occupy the relative position of the cone bodies, they are by no means found in all eyes. The evidence seems to point most strongly in favor o
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