. Animal studies. ^C- w:.. ?A small portion of the radula or tongue-rasp of a snail (Sycotypus). are teem or ridges which also are instrumental in crushing the food, and in numerous minor respects peculiarities exist in differ- ent species according to the nature of the food; but in its general features the digestive tract is similar to that of the clams. The processes of circulation and excretion are also car- ried on by means of systems which show a certain resem- blance to those of the clams. As might be expected, certain differences exist, sometimes very great, but they are of too technica
. Animal studies. ^C- w:.. ?A small portion of the radula or tongue-rasp of a snail (Sycotypus). are teem or ridges which also are instrumental in crushing the food, and in numerous minor respects peculiarities exist in differ- ent species according to the nature of the food; but in its general features the digestive tract is similar to that of the clams. The processes of circulation and excretion are also car- ried on by means of systems which show a certain resem- blance to those of the clams. As might be expected, certain differences exist, sometimes very great, but they are of too technical a nature to concern us further. 96. Sense-organs of lamellibranchs and gasteropoda.— The eyes of mollusks differ widely in their structure and the position they occupy in the body. In our common land snails two pairs of tentacles are borne on the head, the lower acting as feelers, while each of the upper ones bears on its extremity the eye, appearing as a minute black dot (Fig. 54). In this same position the eyes of many marine snails occur, but there are numerous species in which there are other accessory eyes. In many of the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Jordan, David Starr, 1851-1931; Kellogg, Vernon L. [from old catalog].
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Keywords: ., bookauthorjordanda, bookcentury1900, bookdecade1900, bookyear1903
