and other Indigenous Rhizopods. 451 



looking protoplasm with which they are in immediate apposition, 

 beyond what would be produced were they solid substances 

 pressing mechanically on the structure with which they are in 

 contact. As before stated, they never take part in the capture 

 or inception of food, but continue their pulsations uninter- 

 ruptedly even when in close proximity to a food-particle which 

 is being dragged inwards. It is deserving of mention, that on 

 the completion of the systole of the vesicle a depression or pit 

 is temporarily formed, as shown in fig. 3, the surface of which 

 is studded with villous corrugations not unlike those seen in the 

 villous patch of Amoeba villosa ; and further, that, previous to the 

 actual contact of the food-particle with the surface towards 

 which it is being drawn by the cooperation of the surrounding 

 pseudopodia, that portion of the surface, acting under an unex- 

 plained vital impulse, projects its irregular network of sarcode 

 often far beyond the peripheral outHne, to assist in building up 

 the vacuolar cavity. This projection constitutes the " probosci- 

 diform '' apparatus of Ehrenberg. 



Lastly, I have to mention the existence, in the majority of the 

 polygonal cavities, of little clusters of the minutest granules, 

 which during the vigorous condition of the organism are freely 

 suspended by the watery contents, but fall down by their own 

 specific gravity on the death of the creature, and rest passively 

 on the most dependent planes of their polygons. Minute as are 

 the crystalloids of Amoeba, these are still more minute, and 

 hence I have heretofore been unable to determine if they are of 

 similar nature. However, from their appearance, their superad- 

 dition to the mere points that form an integral part of the pro- 

 toplasm, and their uniform size, it is not improbable that these 

 bodies will eventually turn out to be crj'stalloids also. 



Rich as the Hampstead pools have thus been proved to be in 

 facts illustrative of the life-history of the Rhizopods, many others 

 remain to which my limits prevent any allusion being made on 

 the present occasion. I must, however, briefly call attention 

 to two forms of Difflugia that occur abundantly in the same ma- 

 terial as the Amoeba, and which, in like manner, have their tale to 

 tell. In the variety depicted in fig. 12, the test is sometimes 

 made up entirely, as there represented, of minute cylindrical 

 pellets, probably chitinous, but certainly of animal origin. 

 These are placed side by side in very regular order, resting, as it 

 would appear, on a delicate and continuous membranous layer of 

 the same substance. Sometimes, however, a part or the whole 

 of these pellets is superseded by angular particles of sand. So 

 far this form exhibits no novelty. Rut its new and unexpected 

 feature consists in the mouth of the flask-shaped test being de- 

 veloped into a distinct septum and tube, whereby its character at 

 once merges into that of a Dithalamous shell resembling those of 



