8 BIBLIOGRAPHY. 



Although it is scarcely possible to fix with certainty the specific identity 

 of the numerous animalcules enumerated by Leeuwenhoek in the foregoing 

 " Observations '' in various instances, the characters recorded are so well 

 defined as to clearly indicate the generic group to which the organism de- 

 scribed should be relegated. Taking, for example, the first form encoun- 

 tered by him in rain-water, having a globular body with two little anterior 

 horns and a long thread-like tail, which under certain conditions contracted 

 into a spiral form, there can be no question that this type represents some 

 species of Vorticella, or bell-animalcule, and is apparently identical with the 

 form now known by the distinctive title of Vorticella microstomum. While 

 the recorded presence of the two anterior " horn-like processes " appears at 

 first sight to represent a somewhat anomalous structural characteristic, 

 this seeming incongruity vanishes on applying to it the standard of a 

 slightly later acquired knowledge of the members of this infusorial group, 

 and through which medium it is at once made evident that the appendages 

 above referred to as seen by Leeuwenhoek represented merely the imper- 

 fectly defined optical aspect of the lateral edges of the characteristic peri- 

 stomal fringe of cilia. As a remarkable illustration of the manner in which 

 "history repeats itself" even in the annals of scientific discovery, it may be 

 here noted that a precisely similar error of interpretation is associated by 

 Mr. H. J. Carter, close upon two centuries later, in his figure and description of 

 the flagellate organism described in this volume under the name of Salpingceca 

 Carteri (see PI. VI. Fig. 39). The characteristic membranous collar dis- 

 tinctive of this type and its allies, which occupies a position corresponding 

 with that of the ciliary wreath of a Vorticella, is so exceedingly transparent 

 as to be distinctly visible only with the aid of the highest magnifying 

 powers of the modern compound microscope. The structure as observed by 

 Mr. Carter with inadequate magnification, displayed simply its two lateral 

 peripheries, assuming under such conditions the aspect of two projecting 

 ear-like processes, and under which latter designation they are chronicled in 

 the description quoted. The second oval form described by Leeuwenhoek 

 as furnished on the under side with divers incredibly thin feet, and having 

 a soft flexible body capable of assuming a variety of figures, would appear 

 to be a species of Oxytricha, while in the little animal like a mussel-shell, 

 having also on its under side little feet, recorded in the course of his fifth 

 Observation, is at once recognized a form closely allied to, if not specifically 

 identical with the cosmopolitan type Stylonychia mytilus. It is well worthy 

 of note, that while Leeuwenhoek in this first recorded account of the 

 members of the infusorial world more usually associates with them the 

 vague terms of little animals or creatures, he employs for them at the 

 commencement of his discourse that of " animalcula," or, in English, 

 animalcules, generally adopted in conjunction with that of the Infusoria 

 by the majority of later writers. In his observations of various species 

 discovered by him 'in an infusion of pepper we finally find the origin of the 

 burning question of the possible "spontaneous generation " of these minute 



