According to Ehrenberg, the male organs consist, first, of a series of tubular prolonga tions, some of vvhich we have seen are covered with the tremulous gills, and, second, of ve sicles which are capable of contracting. In some cases the tubes are present without the vesicle ; in other cases, as in Ptygura meli eerta (fig. 288. a), the vesicles a reseen but not the tubes. Those who regard these as a male apparatus, suppose that the spermatic fluid is secreted in the tubes, and passed on to the vesicle, where it is projected into the cloaca, and fecundates the ovum. The constant con traction of the vesicle seems opposed to the view that its function is that of merely fecun dating the ovum, and Dujardin thinks it is connected with the function of respiration. Hitherto no spermatozoa have been found in these organs, although Doyere states that he has found zoospores in the tardigrade In fusoria. The spermatic tubes are seen in Rotifer vulgaris (fig. 299. i, i), in Hydatina senta (fig. 293. h ), and Notommata myrmeleo ( fig. 303. f, g).
After the extrusion of the ova from the cloaca in many species, they are attached to the lorica, as in Brachionus pala (fig. 296, f.), in the same way as in some Crustacea. The rapidity with which the ova are produced is very great ; and one individual, in the course of a few days, will be the parent of many mil lions. Their reproductive powers, however, are small compared with those of Polygastria.
In this brief sketch we have occasionally alluded to the affinities of the Rotifera, and we think that there can be little doubt, that these are decidedly with the Articulata stand ing perhaps between the cilio-branchiate'Polyps on the one side, and the Cirrhopoda on the other. Ehrenberg has summed up the general
relations of these creatures in the following manner. They are Polygastria, with a single intestinal canal, without the power of spontaneous fission.
Acalepha, with a simple intestinal canal, and rotatory organs.
Nematoid worms, with rotatory organs and united sexes.
Bryozoa, without gemniiparous reproduc tion.
Molhesca, without vascular pulsations.
Entonwstraca, without pulsation or arti culated feet, and hermaphrodite reproduction.
Fishes without a backbone or a heart, and with rotatory organs and united sexes.
BIBLIOGRAPHY. -- Leeuwenhoek, Philosophical Bibliography -- Leeuwenhoek, Philosophical Transactions, 1701-1704. Baker, Employment of the Microscope. London, 1753. Bory St. Vmeent, Dictionnaire Classigne d'Histoire Naturelle, art. ROTIFERES. Ehrenberg,Infusions-thierchen. Berlin, 1838. Pritchard, Infusoria, living and fossil. London, 1845. Doyere, Memoire sur les Tardigrades ; Ann. des Sc. Nat. 1842. Owen, Lectures on Comparative Anatomy, vol. London, 1843. Grant, Outlines of Comparative Anatomy. London 1843. T. Rymer Jones, A general Outline of the 'Animal Kingdom. London, 1841. Dujardin, Distoire Naturelle des Zoophytes, Infusories. Paris, 1843; Report on the Progress of Zoology, 1842, published by the Ray So ciety. Oken, Phisio-Philosophy, Ray Society, 1847. Mantell, Thoughts on Animalcules. London, 1846. Carpenter, Cyclopa3dia of Natural Science. London, 1847. (Edwin Lankester.)