EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 251 



ductions are the objects of numerous designs, by which it will be shown 

 that those hairs of vertebrata which continue to grow, are provided with 

 an external scaly envelope, and that their interior is homogeneous, 

 fibrous, and sometimes furnished with a canal, whilst, on the contrary, 

 those of definite growth are hollow in the interior, or provided with 

 aeriferous cells, as are feathers, the relation of which, to the hairs of 

 certain Rodents will be easily perceived. The hairs or scales of the Arti- 

 culata are formed essentially of a flattened membranous vesicle, filled 

 with air, and more or less folded or striated. Ivory, teeth, the vibratile 

 cilia of mucous membranes, &c., are also figured as they appear under 

 an excellent microscope. The author has also represented vegetable 

 organs and tissues, woody fibre, vessels, starch, pollen, &c. In the exe- 

 cution of these figures, he has represented the objects, such as they 

 appear to an experienced eye, through a good microscope with magnify- 

 ing powers of 300 to 400 diameters. He has been careful to note the 

 modifications of appearance caused by different modes of clairage, and 

 the greater or less distance of the objective. It is known that the 

 influence of these circumstances may be such that the same object will 

 appear full or empty, convex or concave, to different observers who do 

 not pay sufficient attention to them. 



Several figures are given of the different appearances which one and 

 the same object may present under these circumstances. 



Report on a Memoir by M. Doyere, relative to the Revivification of 

 Tardigrada and Rotifera. Shortly after the existence of swarms of 

 animalculse in water containing organic matters, had been revealed by 

 the microscope, the use of that instrument led to the discovery of 

 another fact, equally unexpected, and more difficult of comprehension, 

 in as much as it still more widely differed from all the results heretofore 

 arrived at from the study of animated beings. In fact, by the examina- 

 tion of dry dust collected from a gutter, Leuwenhoeck ascertained the 

 existence of an animal which, under the influence of desiccation, ceased 

 to move, lost its form, and no longer gave any signs of life, and which, 

 in this condition, appeared to differ in no respect from a dead body, as 

 it were mummified, by being deprived of the fluids necessary for all 

 animal existence, and yet which, after having been preserved for a long 

 period in this dried condition, was restored to life by contact with a 

 drop of water. Leuwenhoeck did not perceive the whole extent of the 

 singular fact which he had thus discovered, with respect to the Rotifer 

 of house roofs, and did not pursue his researches further on this sub- 

 ject; but a phenomenon of this kind could not fail to excite lively 

 curiosity among zoologists, and to give rise to long controversies, as 

 well as to interesting experiments. It may be remarked that the dis- 

 covery of Leuwenhoeck soon ceased to be an isolated fact in science, for 

 Needham announced that the eels of mildewed corn possessed, like the 

 Rotifera, the faculty of reviving after having been completely dried ; and 

 Spallanzani arrived at the same result, after observation, not only of the 

 Rotifera and Anguillula, but also of another microscopic animalcule, to 

 which he gave the name of Tardigrade (R. tardus/J. 



The investigations of this skilful observer were numerous and con- 



