MICROSCOPIC STUDY OF THE CRYPTOGAMIA. 43 



which any individual among the higher Plants consists, has an 

 independent life of its own, besides the " incidental " life which it 

 possesses as a part of the organism at large : and that the 

 doctrine was first proclaimed, that the life-history of the indi- 

 vidual cell is therefore the very first and absolutely indispensable 

 basis, not only for Vegetable Physiology, but (as was even then 

 foreseen by his far-reaching mental vision) for Comparative 

 Physiology in general. The first problem, therefore, which he 

 set himself to investigate, was hoiv does the cell itself originate? 

 It is unfortunate that he should have had recourse for its solu- 

 tion, to some of those cases in which the investigation is attended 

 with peculiar difficulty, instead of making more use of the means 

 and opportunities which the "single-celled" plants afford; and 

 it is doubtless in great part to this cause, that we are to attribute 

 certain fallacies in his results, of which subsequent researches 

 have furnished the correction. 



In no department of Botany, has recent Microscopy been 

 more fertile in curious and important results, than in that which 

 relates to the humblest forms of Cryptogamia that abound not 

 only in our seas, rivers, and lakes, but even more in our marshes, 

 pools, and ditches. For, in the first place, these present us with 

 a number of most beautiful and most varied forms, such as on 

 that account alone are objects of great interest to the Micro- 

 scopist; this is especially the case with the curious group (ranked 

 among Animalcules by Prof. Ehrenberg), which, from the bipar- 

 tite form of their cells, has received the designation of Desmidiece. 

 In another group, that of Diatomacece (also still regarded as Ani- 

 malcules, not only by Ehrenberg, but by many other Naturalists), 

 not only are the forms of the plants often very remarkable, but 

 their surfaces exhibit markings of extraordinary beauty and 

 symmetry, which are among the best " test-objects" that can be 

 employed for the higher powers of the instrument (Chap. IY) : 

 moreover, the membrane of each cell being coated externally 

 with a film of silica, which not only takes its form, but receives 

 the impress of its minutest markings, the siliceous skeletons 

 remain unchanged after the death of the plants which formed 

 them, sometimes accumulating to such an amount, as to give rise 

 to deposits of considerable thickness at the bottoms of the lakes 

 or pools which they inhabit; and similar deposits, commonly 

 designated as beds of "fossil animalcules," are not unfrequently 

 found at a considerable distance from the surface of the ground, 

 on the site of what must have probably once been a lake or estu- 

 ary, occasionally extending over such an area, and reaching to 

 such a depth, as to constitute no insignificant part of the crust 

 of the globe. It is not only in these particulars, however, 

 that the foregoing and other humble Plants have special attrac- 

 tions for the Microscopist ; for the study of their living actions 

 brings to view many phenomena, which are not only well calcu- 

 lated to excite the interest of those who find their chief pleasure 



