. Elements of zoology, to accompany the field and laboratory study of animals. Zoology. 160 ZOOLOGY shells, protrude their elongated appendages, which together form a sort of rake, and pull in particles which happen to l^e floating aljout them. Other species of barnacles attach them- selves to floating seaweed, ship l)ottoms, and whales; under these circumstances, despite their sessile hal)it, the}' enjoy a constant change of locality. Barnacles doubtless gain great protection from the circumstance that they are sessile and enclosed in shells; but their peculiar habits have given rise to certa
. Elements of zoology, to accompany the field and laboratory study of animals. Zoology. 160 ZOOLOGY shells, protrude their elongated appendages, which together form a sort of rake, and pull in particles which happen to l^e floating aljout them. Other species of barnacles attach them- selves to floating seaweed, ship l)ottoms, and whales; under these circumstances, despite their sessile hal)it, the}' enjoy a constant change of locality. Barnacles doubtless gain great protection from the circumstance that they are sessile and enclosed in shells; but their peculiar habits have given rise to certain peculiarities in reproduction. They are hermaphro- ditic ; both male and female germ cells occur in the same individual. Despite this fact, dwarf male individuals are occasionally found inside the shell of the barnacle; these are known as " complemental ; The general form of the barnacles has also become gTeatly modified by their sessile habit, so that they were long regarded as mollusks, until it was shown that the larva^ are almost exactly like those of other Entomostraca. Trilobites ^ are extinct giant Entomostraca, closely allied to Branchiopods. They were im- mensely aliundant in early geo- logic times, and their remains form a large part of certain rocks. The}' had a segmented boch', with bifid appendages and long an- tenna, and their compound eyes were liorne on the great frontal shield. Some of them were nearly half a metre long (Fig. 158). ^ Ha\-ing three Fig. —a restoration of the ventral asijeet of a Trilobite. Note in particular the character of the appendages. After 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 Davenport, Charles Benedict, 1866-1944; Davenport, Gertrude Anna Crotty, 1866- joint author. New York, Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1911
