1872.] 



Modes of Origin of Infusoria eye. 



257 



to fill the delicate cyst in which it was contained. Then the outlines of 

 the embryo gradually became more defined; three or four other, rather large 

 granules appeared in the neighbourhood of the nucleus ; and one crescentic 

 portion of the embryo-mass presented a smooth, glistening, and homoge- 

 neous appearance. No later stages were traced ; and though no move- 

 ments of the embryo as a whole were seen (only movements of the nucleus), 

 there could not be the shadow of a doubt that these bodies represented 

 organisms of some kind, which were developing, not from ova, but by 

 means of changes taking place in the very elements of the pellicle itself. 



The intermediate connecting links between Flagellated Monads on the 

 one hand, and such Ciliated Infusoria as Paramecium and Kolpoda on 

 the other, are undoubtedly such forms as those which were included by 

 Dujardin in his genus Enchelys. They are scarcely larger than many 

 Monads ; they possess the same simple structure, having no trace of an 

 oral aperture, though, like the Monads, they display an internal vacuole, 

 and like them also they may or may not possess a simple nuclear particle. 

 They present the same variations in form which are to be met with 

 amongst Monads ; and they differ from them only by the presence of 

 vibratile cilia over most of their body, iustead of the possession of a 

 single flagellum. They are, moreover, not unfrequently met with in large 

 numbers m situations in which Monads abound. 



Pineau says he has watched the development of organisms of this kind 

 in a pellicle which formed on an infusion of isinglass. The first stages 

 were altogether similar to those which he has described as having taken 

 place in the evolution of Monas lens*. Corpuscles were seen to separate 

 from the embryonic aggregations without a flagellum, though they con- 

 tinued to increase in size, and soon developed a vacuole and nuclear particle 

 in their interior. As they enlarged, they gradually assumed an oval form, 

 though still remaining motionless and devoid of cilia. At last, with very 

 little further increase in size, cilia were developedf, and the organisms 

 gradually displayed the appearance and locomotory powers which have 

 been attributed by Dujardin to the form which he named Enchelys 

 ovata%. 



The organisms previously mentioned have nearly all been minute ; and 

 it has therefore been somewhat difficult to trace their early stages. These 

 difficulties, however, gradually vanish when we come to the investigation 



* Ann. des Sc. Nat. 1845 (Zool.), p. 183. 



t The apparition of cilia is known to be quite sudden in the development of the 

 spore of Vauchcria, and also to be sudden during the development of some Infusoria, 

 as Cienkowski and others have observed. 



\ To another similar solution of isinglass M. Pineau, mindful of the results recorded 

 by Dutrochet, added a few drops of Ainegar ; and he says: — "II ne sj developpa un 

 seul animalcule : mais en revanche elle se couvrit, comme je m'y attendais, d'un foret 

 de moisissures." 



