. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. ROTIFERA. 411 Projecting from the upper part of the ex- ternal tegument, in many species, is a little process, which Ehrenberg calls a spur, or siphon {Jig. 299. d), and which he thinks is connected with the function of respiration, and therefore calls it a respiratory tube. It corresponds with an orifice in some species (Jig. ), which Ehrenberg calls therespira- tory orifice. He has also hinted that they may be connected with the reproductive func- tion. Two of these organs are seen in some of the Notommata and oth
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. ROTIFERA. 411 Projecting from the upper part of the ex- ternal tegument, in many species, is a little process, which Ehrenberg calls a spur, or siphon {Jig. 299. d), and which he thinks is connected with the function of respiration, and therefore calls it a respiratory tube. It corresponds with an orifice in some species (Jig. ), which Ehrenberg calls therespira- tory orifice. He has also hinted that they may be connected with the reproductive func- tion. Two of these organs are seen in some of the Notommata and other genera, and they are sometimes covered with cilia. Dujardin thinks that they resemble more closely the palpi and antennas of the Entomostraca. The rotatory organs, or wheels, must be also regarded as a portion of the tegumentary system. They are fleshy retractile lobes, covered with vibratile cilia, capable of being contracted or expanded at the will of the animal. The movement of the cilia when the lobes are expanded gives the appearance of a wheel moving upon its axis, an appearance which was a source of much wonder to the earlier observers of these creatures. In addi- tion to the vibratile cilia, there are frequently found, on the rotatory lobes, setae, or bristles, which have not the power of moving. This is the case in Floscularia, if, indeed, the organs called rotatory in that genus are truly homologous with the rotatory organs in other species. The true homologue of the rotatory apparatus in Floscularia appears to us to be seated within the external ciliated lobes, where an evidently active motion is constantly going on. The form of the lorica varies greatly ; in some species it is flat and depressed, as in Pterodina and Monostyla; in others it is pris- matic, as in Mastigocerca, or gaping, as in Euchlami {Jig. 294.). Some species, as Ste- phanoceros (Jig. 292.), Floscularia, Melicerta, and others, have a soft skin, very contractile, which secretes externally a case,
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