146 Proceedings of the Royal Ivish Acddemij. 



IS'ot less curious is 'it again, seemingly, hoiv these little bodies 

 remain upon the filament. What power keeps them there ? They never 

 seepa to glide off or to be met with in the water around. ' In fact, 

 these Kttle performers on the "■ slack rope" seem to hold on admirably 

 — ^but then their action is very deliberate ! 



I have sometimes supposed that, surrounding hoth spindles and 

 filaments, a very subtle and delicate sheath, or envelope, must exist, 

 of some amount of contractile power, whose action might exercise a 

 propelling force to urge the spindles along the median axis, or, at 

 least, to act as an auxiliary in conjunction with their inherent con- 

 tractile locomotive power. Under a very high amplification indeed, I 

 have thought to have seen such a delicate envelope, but I cannot say 

 that the appearance might not have been due to an optical illusion. 



However, such a structure would not be without parallel in certain 

 Helizoan Ehizopoda, for instance, Actinosphcerium Eichhornii, in 

 which the radiating pseudopodia possess a central axis of firmer con- 

 sistence (surely not comparable to a spicule), covered by a softer 

 sarcode envelope, certain granules passing between, evidently carried 

 passively by the latter. But the movement of the spindles, consisting, 

 as it does, of a quiet and smooth glide, is of different character. The 

 axis of the pseudopodium of Actiuosphaerium, comparatively speaking, 

 is a much coarser object than the delicate filament upon which the 

 spindles travel in the present organism, and the soft involving gra- 

 nular sarcode of the former is indeed a very palpable thing as com- 

 pared with the very subtle sheath assumed to possibly exist in the 

 latter. 



There exists a certain minute rhizopod, of which I have seen but 

 very few examples, and have therefore had by far too restricted 

 opportunity to study it, to give an account of or to describe it. It is 

 there, however, and even, as is probable, I may not myself be so for- 

 tunate as to re-encounter it, it will most likely be found by other 

 observers, and far better treated of. For the present purpose it is 

 enough to mention that this form is of an orange or buff colour, glo- 

 bose its '' normal" figui-e, but is capable of much alteration of outline, 

 and it is furnished with numerous linear pseudopodia. JSTow, the point 

 worth mentioning here is, that it possesses the power to eject with 

 force, and rapidly, a considerable number, or (one might say) to "fire 

 off" a simultaneous ''volley" of its own orange granules, from all 

 round its periphery, to a distance equal to the length of its pseudo- 

 podia, and with an amount of energy and -consentaneousness which is 

 truly surprising; no sooner, however, have the granules reached a 

 tolerably equidistant limit fi'om the periphery, than they begin to 

 return, but, by comparison, much more slowly, and they become re- 

 absorbed into the general central mass. This ciuious action I have 

 happened to see on only two or three occasions, and under only a low 

 power ; I, of course, immediately turned on a higher power, but the 

 performance so rapidly accomplished was over, nor would the perverse 

 thing repeat it. Other similar forms evince comparable phenomena in 



