3177. Integument (skin). 20 Color Photomicrographs. 1. Skin of dogfish, t.s. placoid scales 2. Skin of frog, t.s. 3. Skin of salamander, t.s. 4. Skin of lizard, t.s. scales 5. Skin of bird, t.s. feather development 6. Human skin from finger tip, t.s. gene