OF THE DESMIDIE^. 9 



at all correct, the statements above quoted respecting the ciliary origin of 

 cyclosis, and more particularly the hypothesis of a vascular system, are 

 scarcely or not in any way admissible. We are disposed to attribute the 

 appearances so intei-preted to misconception. Dr. Wright's notion of canals 

 or vessels is equally extravagant with that once advanced by Schultze, of the 

 network of sap-vessels in and about the cells of plants, and requires no dis- 

 cussion. The opinion of Mr. Osborne that the ciuTcnts in Closteria and other 

 Desmidieae are due to ciha, and are not analogous ^dth the in all respects 

 similar currents in the cells of various aquatic plants, is simply an assump- 

 tion, and one indeed in opposition both to what an unbiassed observation of 

 the phenomenon in the two sets of plants would suggest, and to what com-, 

 parative physiology would teach. Again, the analogy he suggests between 

 his supposed ciliary cyclosis and the ciliaiy action of the branchiae of the 

 mussel will be inconceivable to any one who understands the stnictiu'e of the 

 branchial apparatus of Mollusca, the distribution of the cilia on the external 

 surface of a mucous membrane, and their office there in providing for the 

 active performance of the respiratory function. Analogy would, indeed, in- 

 duce us to beheve, that if cilia are the motory organs of the cyclosis of 

 Desmidieae, they are equally so of that in other unicellular Alga3, as well as 

 of that in the cells composing the tissue of compound forms. If so, we might 

 adopt Mr. Western's belief in the existence of ciha wherever a cii'culation of 

 the contents of cells is visible, did not our opinion of the natm-e of cells and 

 of the histological relations of their parts deter us from accepting the doc- 

 trine at all of the presence of internal cilia within unicellular organisms. 



Then, again, we cannot see the necessity of a ciliary apparatus to secure the 

 fluctuating, oscillating or irregular and mostly incomplete movements of the 

 corpuscles within the cells of Desmidieae. To us such movements are expli- 

 cable by reference to the changes ensuing in the nutritive processes of the 

 living organism, and to the currents caused by the ever-acting endosmose and 

 exosmose. Moreover, it should be borne in mind how exceedingly minute 

 these molecular movements are ; how very inconsiderable the space passed 

 through is ; how sluggish, compared with those due to undoubted ciliary ac- 

 tivity, the movements themselves are. But in addition to arguments deducible 

 from analogy and general morphology, those put forward by Mr. Wenham, 

 resting on direct observation and experiment, seem to us strongly adverse to 

 Mr. Osborne's hypothesis, and indicate it to be a consequence of optical de- 

 ception. At a preceding page (p. 5) we have quoted Mr. Wenham's remarks 

 on the deceptive effects produced in viewing objects by oblique sunlight, or 

 by any powerful source of illumination, and by the use of a large angle of 

 aperture ; we will here add his comparative obseiTation of the circulation of 

 Anacharis. In viewing this, he tells us {op. cit. p. 159), " with a large aper- 

 ture, the chlorophyU-granules traversing along a straight and thin septum (if 

 the position is favourable) appear to project into the neighbouring cell, seem- 

 ing to pass directly under the line of the ceU-waU. Smaller particles will 

 apparently travel within the substance of the cell-wall ; and in case of a 

 boundary or single cell, or in unicellular plants, if the surrounding water has 

 nearly dj'ied up, the rim or prism remaining round the exterior (by the way, 

 just the conditions under which Mr. Western made his obsel'^^ation) causes 

 irregular refracted images of the particles of protoplasm to appear outside the 

 cell, bearing such a remarkable similarity to external cilia, that the passing 

 shadows may even be mistaken for currents in the water." 



Besides the incomplete rotation or circulation of the contents just con- 

 sidered, there is an active bustling sort of movement of minute granules 

 within an apparent globular Tesicle situated at each end of the elongated 



