48 INTRODUCTION. 



Animal Kingdom to the observation of Microscopists furnished 

 with vastly improved instruments of research, it was natural that 

 those minuter forms of Animal life which teem in almost every 

 stationary collection of water, should engage their early atten- 

 tion ; and among those Naturalists who applied themselves to 

 this study, the foremost rank must undoubtedly be assigned to 

 the celebrated German Microscopist, Prof. Ehrenberg. For al- 

 though it is now unquestionable that he has committed numer- 

 ous errors, — many doctrines which at first gained considerable 

 currency on the strength of his high reputation, having now been 

 abandoned by almost every one save their originator, — ^yet when 

 we look at the vast advances which he unquestionably made in 

 our knowledge of Animalcular life, the untiring industry which 

 he has displayed in the study of it, the impulse which he has 

 given to the investigations of others, and the broad foundation 

 which he has laid for their inquiries in the magnificent works in 

 which his own observations are recorded, we cannot but feel that 

 his services have been almost invaluable, since, but for him, this 

 department of microscopic inquiry would certainly have been in 

 a position far behind that to which it has now advanced. Yet, 

 great as has been the labor bestowed by him and by his followers 

 in the same line of pursuit, it has become increasingly evident 

 of late years that our knowledge of Infusoiy Animalcules is still 

 in its infancy ; that the great fabric erected by Prof. Ehrenberg 

 rests upon a most insecure foundation ; and that the Anatomy, 

 Physiology, and systematic arrangement of these beings need to 

 be restudied completely, ab initio. For, in the first place, there 

 can be no doubt whatever, that a considerable section of the so- 

 called Animalcules belongs to the Vegetable kingdom ; consist- 

 ing, as already pointed out, of the motile forms of the humbler 

 Plants, of which a very large proportion pass, at some period of 

 their existence, through a stage of activity that serves for their 

 diflusion. Moreover, in another group, whose character has been 

 entirely misconceived by the great German Microscopist, and 

 was first clearly discriminated by M. Dujardin, there is neither 

 mouth nor stomach of any kind ; the minute plants and animals 

 which serve it as food, being incorporated, as it were, with the 

 soft animal jelly, which constitutes the almost homogeneous 

 body; and this jelly further extending itself into " pseudopodial" 

 prolongations, whereby these alimentary particles are laid hold 

 of and drawn in. It was by the same distinguished French Mi- 

 croscopist, that the important fact was first discovered, that 

 animals of this Rhizopod type are really the fabricators of those 

 minute shells, which, from their Nautilus-like aspect, had been 

 previously regarded as belonging to the highest class of the Mol- 

 luscous Sub-Kingdom ; and the whole of this most interesting 

 group, which had received from M. D'Orbigny (who first per- 

 ceived the speciality of its nature, and made a particular study 

 of it) the designation of Foraminifera, has thus had its place in 



