Page:The American Cyclopædia (1879) Volume VI.djvu/50

 I.KSMARRES . was formerly classed near the diirerini: i" having two very small the two great incisors of the Desman (Mygale Pyrenaica). lower j:iv. and in the two upper triangular and Battened incisors. The M. (0.) Pyrenaica is n.t Hindi more than half the size of the Russian species ; it is found in southern France, in the di>trict of the Pyrenees. DESMARRES, Louis Angnste, a French oculist, born in Brreox in 1810. He studied at the Sorbonne, and devoted himself entirely to the treatment of diseases of the eye, and soon ac- quired a great reputation. He has contributed largely to a better understanding of the pathol- ogy and anatomy of the eye, and invented an ophthalmoscope which is now in general use among practitioners. His Memoire sur une 'a method* d' employer le nitrate d 1 argent iet'/ne* ophthalmic* (1842) and Emploi de la belladonne dans let perforations de la cornee, excited special attention ; but his most important work is his Traite theorique et pra- -x iinil.nlics dts yeux (1847), which he considerably enlarged in subsequent editions, and which i- ron-idered a standard authority on the subject. DESMIDIILE, minute algrc, or protophytes, which grow in fresh water, and whose forms singularly beautiful appearances under the microscope. For a long time claimed both a-* animals and plants, they seem to stand on the limits of either kingdom. The controversy as to their true place has enlisted a great num- observers, who have submitted every fact to tht; nn st rigorous examination. Ehren- i them as animalcules; Dalrymple tended observations upon a single genus . which appeared to him to indicate animality ; and Prof. Bailey and C. Eckhard U the same conclusion. The latter de- -'innent for their being animals partly from their motion, partly from their i. Khreiiheri: has not only given itic descriptions of these questionable animals or plants, hut his own observations, 1 with those of his predecessors, upon t'th.-sr bodies, will he found copi- ously detailed hy him. It is, however, apparent DESMIDIE^E that all the facts known upon the subject are interpreted as if these creations were undoubt- edly animals, while the same facts would bear a very different signification if we proceeded upon the supposition that they are plants. Meyen contended for the vegetable character of the desmidieoe, and was the first to detect starch in the cells; and the accuracy of his remarks was fully confirmed by Ralfs, Jenner, and other recent algologists. It is said that no starch is to be detected in the young cell, while upon the growth of the sporangium, or spore capsule, it appears and increases rapidly, as in the seeds of the higher plants, in which it generally abounds. Of all the circumstances which indicate the vegetable nature of the des- midieze, this is the most important, since it can be so easily submitted to experiment. In cer- tain cavities in closterium Dalrymple noticed a peculiar motion of molecules on which he laid some stress. This motion has been termed swarming, on account of the commotion which arises within the cell ; as the disturbance in- creases, the cell opens, when the molecules, or rather germinative cells, dart about in every direction, until at length they settle down into repose. The presence and functions of these cells in plants of entirely differing families and groups, render their occurrence in those under consideration no evidence of their being ani- mals. The desmidieaa resist decomposition, exhale oxygen on exposure to the sun, preserve the purity of the water containing them, and when burned do not emit the peculiar odor usually so characteristic of animal combustion. Berkeley, in his " Introduction to Cryptoga- mic Botany," remarks that if in some points there be anomalies, as in closterium, their whole history is so evidently vegetable, their mode of increase, growth, &c., that if we refuse them the title of vegetables, we may as well dispute that of the whole tribe of protophytes. The fact that under the influence of light they give out oxygen, added to the other character- istics, is quite convincing. Considering the desmidiese as vegetable productions, we find them peculiar for their beauty, variety of forms, and external markings and appendages. They are' mostly of an herbaceous green color, and contain a green internal matter. The frond divides into two valves or segments, by a sort of voluntary action ; a mode of growth in the bisection of cells that Meyen and others have proved to be frequent if not universal in the more simple algse. In the desmidieao the multiplication of the cells by repeated division is full of interest. The compressed and deeply constricted cells of euastrum offer most favora- ble opportunities for ascertaining the manner of this division; for although the frond is really a single cell, yet this cell in all its stages appears like two, the segments being always distinct. As the connecting portion is so small, and necessarily produces the new seg- ments, which cannot arise from a broader base than its opening, these are at first very minute,
 * tin- teeth, however, are like those Of