58 THE MICROSCOPE AND ITS KEVELATIOISTS. 



its interior, that is attached by one extremity to the interior of the sac, 

 and vibrates with a quick undulatory motion in its cavity; and there can 

 be little doubt that their function is to keep up a constant movement in 

 the contents of the aquiferous tubes, whereby fresh water may be contin- 

 ually introduced from without for the aeration of the fluids of the body. l 

 The Nervous system is represented by only a single ganglionic body 

 (sometimes bilobed, however), which lies at one side of the oesophagus, 

 in near proximity to the eye-spots, the spur-like organ, and the ciliated 

 pit, and has also, in some Rotifers, an auditory vesicle attached to it. 

 No nerve-trunks proceeding to the muscular bands have as yet been cer- 

 tainly distinguished. 



450. The Keproduction of the Rotifera has not yet been completely 

 elucidated. Although they were affirmed by Prof. Ehrenberg to be herm- 

 aphrodite, yet the existence of distinct sexes has been detected in so 

 many genera (for the most part by Mr. Gosse a ), that it may fairly be 

 presumed to be the general fact. The male is inferior in size to the fe- 

 male; and sometimes differs so much in organization, that it would not 

 be recognized as belonging to the same species, if the copulative act had 

 not been witnessed. In all the cases yet known, as in the Asplanclma of 

 which the separate male was the first discovered, there is an absolute and 

 universal atrophy of the digestive system; neither mastax, jaws, oesopha- 

 gus, stomach, nor intestines being discoverable in any male; no other 

 organs, in fact, being fully developed, than those of generation. The 

 male would appear, therefore, quite unfit to obtain aliment for itself; 

 and its existence is probably a very brief one, being continued only so 

 long as the store of nutriment supplied by the egg remains unexhausted. 

 In the remarkable six-limbed Rotifer discovered by Dr. Hudson, and 

 named by him Pedalion mira, the virgin female was found to lay female 

 eggs during the greater part of the year, while male eggs, which are not 

 found in the same individuals, " are half the size of the female ones, and 

 are carried in clusters of often a score at a time." The males are very 

 small in comparison with the females, and are very short-lived, sometimes 

 dying within an hour. In Rotifer, however, as in a large proportion of 

 the group, no males have yet been discovered, probably because they are 

 produced only at certain times. The female organ consists of a single 

 ovarian sac, which frequently occupies a large part of the cavity of the 

 body, and opens at its lower end by a narrow orifice into the cloaca. 

 Although the number of eggs in these animals is so small, yet the rapid- 

 ity with which the whole process of their development and maturation is 

 accomplished, renders the multiplication of the race very rapid. The 

 egg of the Hi/datina is extruded from the cloaca within a few hours after 

 the first rudiment of it is visible; and within twelve hours more the 

 shell bursts, and the young animal comes forth. Three or four eggs 

 being deposited at once, it was calculated by Prof. Ehrenberg that nearly 

 seventeen millions may be produced within twenty-four days from a sin- 

 gle individual. In Rotifer and several other genera, the development of 

 the embryo takes-place whilst the egg is yet retained within the body of 

 the parent (Fig. 310, k), and the young are extruded alive; whilst in 



1 See Prof. Huxley's account of these organs in his description of Lacinularia 

 socialis, "Transact, of Microsc. Soc.," N.S., Vol. i. (1853), p. 1. 



2 " Philosophical Transactions," 1853, p. 313. Seealso Dr. Hudson in ; ' Monthly 

 Microsc. Journ.," Vol. xiii. (1875), p. 45. 



3 " Monthly Microsc. Journ.," Vol. viii. (1872), p. 209; and " Quart. Journ. Mic. 

 Sci.," Vol. xii. (1872), p. 333. 



