Eyes absent. 



Eyes present. 



ROTIFERA. 



Analysis of the genera. 

 With proboscis,~and appendi- 



407 



cular processes on foot. 



[Wheels pedunculated. 

 [Wheels sessile. 



fTwo toes 

 Foot with processes. J Three 



No proboscis or processes. 



Two frontal eyes. . 

 Two cervical eyes. 



Foot without processes. 



Two toes. 



Callidina. 



Hydrias. 

 Typhlina. 



Rotifer. 

 Actinurus. 



Monolabis. 

 PhUodina. 



This family, which includes the true Ro- 

 tifers of Dujardin, embraces some of the least 

 known, as also the most common, animals of 

 the class. The genera Hydrias and Typhlina 

 were found during the travels of Ehrenberg 

 in Asia. Callidina and Monolabis have been 

 found by Ehrenberg at Berlin only. The 

 Rotifer vulgaris was the first wheel-animalcule 

 ever seen, and is certainly the most com- 

 mon of the whole class. It was described 

 with great accuracy by Leeuwenhoek in 

 in his early papers on its discovery. It is 

 this animal which has also been most fre- 

 quently the subject of the desiccating ex- 

 periments to which we have alluded. Acti- 

 nurus Ncptunius was known to the earlier 

 observers of these creatures as the wheel- 

 animalcule with the long foot, on account of 

 the extension of its foot or tail. The Pkilo- 

 dina, though not an unfrequent genus, was 

 first described by Ehrenberg in 1838. The 

 articulated character of the integument in the 

 apecies of this family, give them a habit dif- 

 ferent from the rest of the group : by means 

 of their probiscoid mouth and prehensile tail, 

 they can successively grasp the object on 

 which they are placed, and are thus enabled 

 to crawl in the same way as the leech and 

 other Annulosa. The affinity between the 

 Rotifera? proper and the Arctiscon and whole 

 family of Tardigrades, which are not ad- 

 mitted as Infusoria by Ehrenberg, has been 

 pointed out by Doyere ; and there can be little 

 doubt that we have, through this group, 

 a transition from the Rotiferae to the Anne- 

 lida. 



The Rotifer vulgaris is found very com- 

 monly in the ponds and ditches of England, 

 where it attaches itself to the Conferva?, the 

 various species of Lemna, and the Cerato- 

 phyllum, which are so abundant in these 

 places. M. Morren, of Liege, has recently 

 pointed out a curious habitat for this animal. 

 Reaper, many years ago, observed that this 

 animalcule sometimes penetrated the cells of 

 Sphagnum, and even lived in those parts of 

 the plant which were not immersed in water. 

 Unger described, in 1828, some vesicles in 

 the structure of Vaucheria clavata, which had 

 the power of moving about spontaneously, 

 and which he discovered were produced by an 

 animalcule in their interior. The subsequent 

 researches of Morren showed that this ani- 

 malcule was truly the Rotifer vulgaris. It 

 seems to prefer such a situation to its liberty, 

 for Morren says, " One day 1 opened a protu- 

 berance gently ; I waited to see the Rotifer 

 spring out and enjoy the liberty so dear to all 

 creatures, even to imprisoned animals ; but 



no, he preferred to bury himself in his prison, 

 descending into the tubes of the plant, and to 

 nestle himself in the middle of a mass of 

 green matter, rather than swim about freely in 

 the neighbourhood of his dwelling." 



The species of PhUodina are beautiful ani- 

 malcules. P. roseola has a rose colour of its 

 whole body ; and the ova, when deposited, 

 have a reddish colour. The ova of this ani- 

 malcule are deposited in little heaps, which 

 the parent attends to, and even remains with 

 the young ones after they are hatched, which 

 Ehrenberg attributes to a kind of social in- 

 stinct. Professor Agassiz found this creature 

 amongst the animalcules which contribute to 

 the colour of the red snow. It was at one 

 time supposed that this colour was due to a 

 species of Alga, the Protococcus nivalis. Mr. 

 Shuttleworth, of Berne, was the first to an- 

 nounce that he had found, in addition to the 

 cells of a plant, several species of Polygastria, 

 belonging probably to the genus Astasia. 

 Subsequently to this announcement, Professor 

 Agassiz discovered the presence of this ani- 

 malcule in the same situation. The author of 

 this article has found PhUodina roseola in com- 

 pany with a red animalcule, apparently a 

 species of Astasia, in waters slightly im- 

 pregnated with sulphuretted hydrogen. Ehren- 

 berg says this animal sometimes occurs entirely 

 colourless, so that its colour may depend on 

 its food. 



Family 8; BRACHION.EA. Character. 

 Loricated Rotifers, with a double rotatory 

 organ. 



The external covering of these animals is a 

 testula, such as is possessed by the tortoises, 

 not a scutellum, as found in the Crustacea. 

 The motory system consists partly of external 

 organs, and partly of internal muscles. The 

 rotatory apparatus is often apparently com- 

 posed of five parts three in the middle and 

 one on each side. The latter only can be 

 regarded as the true rotatory organs ; the 

 middle portions are only ciliated frontal pro- 

 cesses. In the genus Synchceta there are two 

 setae in the rotatory organs, which are also 

 possessed by the Brachionsea. Noteus and 

 Brachionus have a furcate foot, Anurcea is foot- 

 less, and Plcrodina has a kind of sucker in its 

 place. The nutritive organs are very similar 

 to those of the Hydatinaea and Euchlanidota. 

 Intestinal glands have been observed in all 

 the species. The reproductive organs consist 

 of an ovarium, with a few large eggs, which 

 are not hatched internally, but, with the ex- 

 ception of Pterodina, are externally attached 

 to the parent after expulsion. The male 

 organs consist of glands and contractile vesi- 



D D 4f 



