OF THE ROTATOEIA. 441 



stiuct ; some so supposed are simply acts dictated by external circumstances. 

 Perty intimates that the apparent sinking after one another, the gamboling 

 among themselves, and the fact of their depositing theii' eggs in chosen and ap- 

 propriate localities, to which, after an absence, they will return, are pheno- 

 mena evidencing perception, design, and a sense of company. This last imagined 

 sense was one suggested by Ehrenberg, who affirmed that he had observed it 

 in the case of Philodina roseola, which, when kept in glasses, deposited its 

 eggs in heaps, the parent remaining a long time with the young ones pro- 

 duced from them, and so constituting a sort of family or colony, — an act 

 dictated, as he sm^mised, by a sense of company or family. 



The occasionally-observed rejection, and ejection, of what may be deemed 

 disagreeable or unsuitable nutriment, are acts which some might interpret to 

 be indicative of volition, and, in some degree, of pain or unpleasant impression ; 

 but they are quite explicable without reference to a sentient nei-ve- centre, or 

 to high psychical endowments. The same thing may be said of other reputed 

 evidences of the existence of psychical or mental faculties. 



Of the Repeoductive Organs and Development of Eotatoeia. — The 

 Rotatoria were for a long time assumed to be hermaphrodite or monoecious, 

 ?. e. that each individual possessed a perfect male and female reproductive 

 apparatus, by which ova are formed, and fructified without the presence or 

 contact of any other individual. There has never been any difficulty in 

 determining the female generative organs, which are very clear and well 

 defined ; but the greatest diversity of opinion has subsisted respecting the 

 coexistence of male and female organs in the same individual. 



Dujardin attempted no explanation of this matter, whilst Siebold candidly 

 affirmed that in the absence of any precise knowledge as to the male organs, 

 it is impossible to say whether the Rotatoria are monoecious, or have the sexes 

 separate — are dioecious. 



The clearing up of this quest io vexata, in several at least of the Rotatoria, 

 is due to our coimtryman Sir. Brightwell of Norwich, who demonstrated the 

 existence of distinct male animals, and figured them (XII. Q5, QQ) in his 

 ' Fauna Infusoria.' This discovery was further carried out by Mi\ Dal- 

 rymple, and has subsequently been extended by Mr. Gosse, Leydig, and 

 others. Inasmuch, however, as the monoecious or hermaphi^odite condition 

 is very prevalent among the lower Invert ebrata ; as the males of the majority 

 of the Rotatoria have as yet escaped detection ; and as there are parts dis- 

 cernible in several of them presenting some similarity with recognized male 

 organs in other animals, not a few eminent observers still incline to the 

 belief that, at least in a portion of this class, the sexual organization is of the 

 monoecious t}^3e. These doubtful organs wiU be discussed after the well- 

 determined female apparatus, and the male animals, have been described. 



Female Repeoductive Oegans. — These were pretty accurately determined 

 by Ehrenberg, who noticed a single or double ovary, an oviduct, an ovisac, 

 and a vaginal sheath or outlet leading to the cloaca or the rectum. 



The ovary, in which the ova or eggs are generated, hes immediately beneath 

 or behind the alimentary canal, between it and the contractile sac (XXXVIII. 

 26 0, p ; XXXYII. le, 12 Ti, 32 c) ; its anterior border often advances as far 

 forward as the maxjUary (oesophageal) head. Oftentimes its position is rather 

 transverse, and it lies across the intestine, or is curved to some extent around 

 it. It varies in size, but is always a very large organ, and occupies a consider- 

 able space in the interior of the body. It also presents much diversity of 

 figure, being sometimes round, oblong, or oval, at others flattened, elongated, 

 reniform, bilobed, horned, or curved like a horse-shoe. It is enveloped by 

 a dehcate membrane, rendered verv obvious by the action of acetic acid 



