have often watched a single such granule caught in and carried along by the current of the flowing sap, up towards the cavity at the end, and down again towards the centre, which it reached only to again pass on up, or was arrested in its course and stopped by the way. Again I have often observed that whilst these granules were in themselves passive, and appeared to be but carried along by the stream, and were at the same time all but colorless, the uneasy little dots at the ends of the frustule were in themselves motive, and usually more or less colored, generally of a light brown tint. However this may not be always the case as we cannot, for certain, reason as to what would take place under particular circumstances in the vegetable kingdom, from what we see occurring during the prevalence of peculiar conditions. The current within individuals of Closterium, and its allied genus Penium, as they have been observed by me, would seem to be from the middle towards the ends externally, or against the primordial utricle, and then turning upon itself down again beneath or interiorly against the mass of endochrome in and along the lighter colored interspaces of that mass, which cause it to assume the coarsely banded appearance so very commonly to be seen. One observer, named Osborne, has thought that this circulation of fluid within the Desmids-for it is by no means peculiar to Closterium or even Penium, but can be observed in several genera, although not so markedly as in these two -is caused by the waving about of little hairs, or ciliæ, as they are called, from their resemblance to eyelashes, set upon the frustule both within and without its cell-wall; but hardly any one else has been able to see any such ciliæ, and an excellent authority upon the microscope, Dr. Carpenter, says, "although the circulation is an unquestionable fact, yet I have no hesitation in regarding the appearance of ciliary action as an optical illusion due to the play of the peculiar light employed among the moving particles of the fluid; the appearance which has been thus in terpreted being producible at will by a particular adjustment of the illumination, but being undiscoverable when the greatest care is taken to avoid sources of fallacy." Mr. Osborne also thought he had detected external apertures in the cell-wall of Closterium, at about the locality where Ehrenberg had placed his "prehensile organs," or "feet," which, of course, were necessarily present, whilst he considered the Desmids as animals. Dr. Carpenter says with regard to this, "I must confess to a similar scepticism respecting the external apertures said by Mr. Osborne to exist at the extremities of Closterium; for whilst their existence is highly improbable on a priori ground, Mr. Wenham (than whom no observer is entitled to more credit) states that 'not the slightest break can be discovered in the laminated structure that the thickened ends display."" My observations coincide exactly with those of the last gentlemen, and in fact the same is the opinion of all competent and unprejudiced observers at the present day. Most, if not all the Desmids, have the power of changing their place by sailing, slowly it is true, through the water, though not exhibiting the liveliness so evident in the Diatoms. But that they do move can be shown by shaking them up with some mud, and then covering them with water in a saucer, and placing them where the direct sunlight, or even light reflected from the sky, can fall upon the surface, when, after a time, it will be seen to become green, and the Desmids are found to have congregated at the point nearest the light; in this respect exhibiting their vegetable nature, for we know that plants love the light and will tend towards it whenever they can do so. An individual of Closterium is represented in Plate 5, fig. 10, and the vacuoles at the ends containing the motile granules are there seen, as well as indications of the circulation of the cell-contents spoken of. The mode of growth and reproduction of the Desmids are very remarkable and of great interest, but we must leave the consideration of them to some future time, only now referring to our plate, where several forms of these beautiful plants are represented illustrating the grace and symmetry exhibited in these simple organisms. THE HARRIS CORRESPONDENCE.*- Well do we remember the delight and lively interest we felt when for the first time we were allowed to look over the Harris manuscripts, after they came into the possession of the Boston Society of Natural History. There were fles of letters from Curtis, Doubleday, Hentz, Leconte and Herrick, with notes from entomologists of greater celebrity, and others of lesser fame, with a number of manuscript books filled with long extracts from the works of Godart, Latreille and Olivier, in the concise and beautiful handwriting of this painstaking and precise man; copies of his own letters to his correspondents, illustrated with occasional pen and ink sketches, often of unusual fidelity and finish, of which we have fac-similes in the work before us, and three volumes of drawings, plain and colored, often made with great care, - all evidences of great industry and ability, and of the highest interest to a young naturalist away from instructors of eminence, as showing the methods of studying natural history, — being the chips, models and half-finished undertakings of a working naturalist. Such is the Harris Correspondence, and we have said nothing of the qualities of heart, the geniality, strong human sympathies and undying love of nature that crop out in the letters, published and unpublished, of one who, all in all, must rank as the first among American entomologists. In this very attractive volume, adorned with an excellent portrait on Entomological Correspondence of T. W. Harris, M. D. sional Papers of the Boston Society of Natural History. I. To be had of the Naturalist's Book Agency. Edited by S. H. Scudder. Occa- |