REPRODUCTION OF ROTIFERA. 475 



aeration of the fluids of the body.* — There is much uncertainty with 

 regard to the structures which Prof. Ehrenberg has described as 

 Ganglia and Nerves ; and it seems doubtful if there is more than 

 a single nervous centre in the neighbourhood of the single, double, 

 or multiple red spots, which are seen upon the head of the 

 Rotifera, and which, corresponding precisely in situation with 

 those that in the higher Articulata are unquestionably eyes, are 

 probably to be regarded as rudiments of Visual organs. 



360. The Reproduction of the Rotifera has not 'yet been com- 

 pletely elucidated. There is no instance, in this group, in which 

 multiplication by external gemmation or spontaneous fission is 

 certainly known to take place ; but the occurrence of clusters 

 formed by the aggregation of a number of individuals of Cono- 

 chilus, adherent by their tails, and enclosed within a common 

 lorica, would seem to indicate that these clusters, like the aggre- 

 gations of Polygastrica, Bryozoa, and Tunicata, must have been 

 formed by continuous growth from a single individual. It will 

 be presently shown, moreover, that there is strong reason for the 

 belief that what are commonly termed ' eggs ' are really internal 

 gemmae. Although the Rotifera were affirmed by Prof. Ehren- 

 berg to be hermaphrodite, yet the existence of distinct Sexes has 

 been detected in so many genera (for the most part by Mr. Grosse +), 

 that it may fairly be presumed to be the general fact. The Male 

 is inferior in size to the female, 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 Asplanchna, whose separate male 

 was first discovered by Mr. Brightwell in 1848, there is an abso- 

 lute and universal atrophy of the digestive system ; neither mas- 

 tax, jaws, oesophagus, stomach, nor intestines, being discoverable 

 in any male ; in fact, no other organs being fully developed than 

 those of generation. It 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 Rotifer, however, 

 as in by far the larger proportion of the class, no males have 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 

 rapidity with which the whole process of their development and 



* See Mr. Huxley's account of these organs, in his description of 

 Lacinularia socialis, "Transact, of Microsc. Soc," Ser. 2, Vol. i. — Other 

 observers have supposed that the pyriform sacs communicate with the 

 general cavity of the body ; but the Author has much confidence in the 

 correctness of Mr. Huxley's statements on this point. 



f " Philosophical Transactions," 1857. 



