. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Heteropygii. 66 BLIND VERTEBRATES AND THEIR EYES. It is thus seen that almost every nook available has been taken possession of by these diminutive fishes. All of them have the two ventrals united along the median line and a thin membrane stretched across their bases to form a pouch. By appressing the ventrals and then raising them, a partial vacuum is formed in this pouch and the fish is enabled to cling to any substance with which its ventral happens to be in contact. In confinement the blind fish frequently util
. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Heteropygii. 66 BLIND VERTEBRATES AND THEIR EYES. It is thus seen that almost every nook available has been taken possession of by these diminutive fishes. All of them have the two ventrals united along the median line and a thin membrane stretched across their bases to form a pouch. By appressing the ventrals and then raising them, a partial vacuum is formed in this pouch and the fish is enabled to cling to any substance with which its ventral happens to be in contact. In confinement the blind fish frequently utilizes the surface of the water of an aquarium for a surface of attachment. All the species in the bay have the habit, if disturbed, of hiding in crab or clam holes. Clevelandia will sit on its tail and pectorals until the hand is near it; then with a quickness which would do honor to a Johnnie Darter, with a flirt of the tail and a stroke of the pectoral, it disappears into its hole, from which, how- ever, it at once thrusts its head to await developments. Several of them frequently take refuge in the same hole. Gillichthys is the largest of these gobies. About San Diego the young are abundant throughout the year. The adult can be caught with hook and line in quantities, especially just at the return of tide during summer. Toward their spawning season they retire to their respective crab holes, and no morsel, how- ever tempting, will lure them forth. At San Diego they begin to spawn about the. Fig. 26. {a) Typhlogobius californiemis Steind. From base of Point Loma. (6) Typklogobius about 25 mm. long. end of March. The young, when first observed, have but few color cells. They are very active, jumping several times their own length if left dry in a watch crystal. The young of this species but little resemble the adult. The maxillary does not reach beyond the eye, the color is in more or less well-defined crossbars, and the scales, which in the adult are cycloid, have several larg
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