. Zoology : for students and general readers . Zoology. 176 ZOOLOOT. Class III.—Rotatoria {Rotifers). General Characters of Rotifers.—The Rotifers, or wheel- animalcules, are abundant in standing water, in damp moss, etc., and in the ocean, and are so transparent that their in- ternal anatomy can be studied without dissection, while they are so minute, being from one fortieth to three hundredths of an inch in length (f to f mm.), that high powers of the microscope are needed in studying them. They are of special interest from the fact that after being dried for months to such a degi-ee that li
. Zoology : for students and general readers . Zoology. 176 ZOOLOOT. Class III.—Rotatoria {Rotifers). General Characters of Rotifers.—The Rotifers, or wheel- animalcules, are abundant in standing water, in damp moss, etc., and in the ocean, and are so transparent that their in- ternal anatomy can be studied without dissection, while they are so minute, being from one fortieth to three hundredths of an inch in length (f to f mm.), that high powers of the microscope are needed in studying them. They are of special interest from the fact that after being dried for months to such a degi-ee that little if any moisture is left in the body, they may be revived and become active. Pro- fessor Owen has observed the revivification of a Rotifer after having been kept for four years in dry sand. As an example of the ordinary type of Rotifer we may cite Squamella magnifled 200 oUongci (Fig. 121), which is allied to BracMonus. The characteristic organ of the wheel-animalcules is the velum (lb) or pair. Pig. Vi\.—Squamella dblcmqa diameters. A view from below; shell or cara- pace (5, -s^ 5^); 5, the aDterior transverse edge of the carapace ; s', the anterior, and .s^, the posterior corners of the carapace; ."J^, the border of the oval, flat area which occupies the lower face of the carapace ; Ih, the cilia-bearing velam of the head; t, the fork of the tail (I') ; m, the mouth ;,;', jaws ; ./•, muscles which move ,; ; st. ix ; CT, the co the excretory syste: c^'^, ni*, the left excretory vessels; eg, eg , two largely developed young.—After Clark, tomacii; a>, the'contractile vesicle, or heart of of ciliated wheel-like flaiJS ystem; ct', c??2^ the right, and i . ^ „ ,, , \ - on each side of the head, which is comparable to the velum of the larval mollusk. By means of the rotatory movements of this velum the creature is whirled swiftly around. The body is broad and flattened, with the walls often dense, chitinous, sometimes shell-like, and variously sculptured, or
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
