Zöology; a textbook for colleges and universities . After Bulletin American Museum of Natural History FIG. 61. Pyramidula ralslonensis, a fossil snail from the Eocene of Wyoming. Enlarged about five diameters. structure of garden or greenhouse snail, we observe that the body,when extruded from the shell, is elongated, with thehead at one end. There is always, of course, a portionof the animal within the shell. The flat surface onwhich the animal moves is called the foot, and the move-ment is by wavelike undulations, as can be seen if thesnail is caused to walk on a piece of glass. It is diffic
Zöology; a textbook for colleges and universities . After Bulletin American Museum of Natural History FIG. 61. Pyramidula ralslonensis, a fossil snail from the Eocene of Wyoming. Enlarged about five diameters. structure of garden or greenhouse snail, we observe that the body,when extruded from the shell, is elongated, with thehead at one end. There is always, of course, a portionof the animal within the shell. The flat surface onwhich the animal moves is called the foot, and the move-ment is by wavelike undulations, as can be seen if thesnail is caused to walk on a piece of glass. It is difficultat first to believe that the substance of the foot is notflowing from one end to the other, just as waves on theocean give the appearance of masses of water movingrapidly forward. As the snail moves, slime is secretedby the slime glands, and thus the creature travels on atrack of its own laying. The head is marked by fourtentacles, the upper long ones bearing eyes at the eye-bearing tentacles can be retracted by thecontraction of inte
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1920
