28 Salt Marshes and their Inhabitants. 



yards in extent, disposes itself in numberless tiny crests and 

 undulations, which give an effect of exceeding richness to the 

 rock surface. This plant is V. cwspitosa, that of the salt 

 marshes, V. velutina. While speaking of Yaucheria we may 

 briefly allude to the remarkable fact that living animals (Roti- 

 fcra) have been repeatedly observed in the interior of the 

 filaments, nor is there much difficulty in accounting for their 

 presence in so unwonted a situation. When the tube of the 

 plant ruptures to allow of the escape of a spore, or from any 

 other cause, the opening so formed would be amply sufficient 

 to allow of the ingress of a rotifer, either as an egg or in the 

 mature state, and when once established in the filament there 

 is nothing to prevent the animalcule breeding ad libitum, so that 

 plants have been observed to be completely colonized by 

 Entozoa of this kind. Intermixed with the marsh Yaucheria 

 we often find a species of Oscillatoria, an alga composed of 

 slender, unbranched, tortuous threads, which are faintly marked 

 by close transverse strias. Its filaments are of microscopic 

 dimensions, being only one two-thousandth of an inch in 

 diameter, and when viewed under the microscope they exhibit 

 plainly the peculiar Oscillatory and worm-like motions from 

 which the genus derives its name. The origin of these move- 

 ments is not thoroughly understood. They had been supposed 

 to be ducto ciliary action (a very convenient explanation by 

 the way, of all sorts of anomalous, ill-understood movements), 

 but are more probably referable to some contractility inherent 

 in the tissue of the plant, perhaps analogous to that which we 

 see in the sarcode of Ehizopoda, etc. At all events, no cilia 

 adequate to produce such motions have yet been defected in 

 Oscillatorias, and the motions themselves are very different in 

 character from those which Ave know to be caused by ciliary 

 action, such as the rotation of Yolvox and the spores of many 

 algas. I am at a loss to conceive how any observant scientific 

 man could explain these motions (or attempt to explain them), 

 as Dr. Hassell has done, in the following words : — " The phe- 

 nomenon of oscillation is due to a certain degree of elasticity 

 belonging to the filaments, which leads to the effort, on their 

 part, whenever, as on being placed for observation on the field 

 of the microscope, must be the case, they are bent or put out 

 of a straight line, bo recover that position which is natural to 

 them. This elastic properly of the iilainent currents, almost 

 imperceptible in the liquid in which they are immersed, and 

 perhaps unequal attractions amongst the filaments themselves, 



are causes amply sufficient fco explain any motion which I have 



ever witnessed amongst the Oscillatori®, and which motion I 



cannot help thinking to have been misunderstood and cx- 

 Brated to such an extent, as to throw around these plants 



