sympathetically-minded naturalist, that of the large number of subsequent writers on ameboid movement only one (Penard, ’02, p. 63) seems to have noticed these folds. Leidy says that “ ... the main trunk and larger pseudopods of the same ameba (_proteus_) assumed more or less the appearance of being longitudinally folded. The endosarc axially flowed as if in the interior of thick walled canals, of which the walls appeared to be composed of finer granular matter with scattered imbedded crystals. In the flow, all the contents did not move with the same rapidity, and usually the smaller particles were swept quickly by the larger ones. Other matter, including some of the largest elements appeared to stick to the inner surface of the extemporaneous tubes, but successively became detached to be carried along with the rest of the contents (p. 46).” “The endosarc appeared to flow within thick walls of ectosarc which often seemed to be longitudinally folded (p. 326).” Penard (’02) confirms Leidy’s observation as to the existence of these folds: “The current (of endoplasm) indeed is not unified, but there exist many currents at the same time because of the fact that the endosarc is divided into a certain number of longitudinal canals or grooves by dense walls, which are of a temporary nature, being broken down and built up from time to time. It is easy to distinguish one canal from the other in this species, the currents being at first more or less parallel, but terminating at the forward end, by their coalescence, as a single mass of liquid (p. 63).” But Penard questions Leidy’s conclusion that the walls are of ectoplasm: “Moreover Leidy deceives himself without any doubt in considering these partitions as folds of the _ectosarc_. The latter, in the rhizopods, is not a special substance, it is a plasma of surface, specialized for the functions which it has to perform, capable of modification as to its intimate structure, but only so temporarily (p. 63).” Although it is a very simple matter to prove to one’s satisfaction the mere existence of these folds--a few minutes’ observation under the high power of the microscope will do that--it is a much more difficult matter to observe how these folds originate, because of the incessant changes going on, as recorded by Leidy. Very young or small pseudopods in _proteus_ have the same general appearance as the pseudopods of other large species (_dubia_, _laureata_, _discoides_, _annulata_, etc.); that is, there is a central axial stream of endoplasm surrounded by a layer of ectoplasm. But there is one difference even here, and that is the greater thickness of the ectoplasmic walls in _proteus_ in proportion to the diameter of the pseudopod. The ectoplasmic tube however is not solid throughout, but is more or less honeycombed, somewhat like a network, with the spaces filled by endoplasm.