dant in the brown "growth," with which the bottom was strewn. With the food thus distributed, the worm-like shape was doubtless well adapted to the situation. On the other hand, in those dishes containing no sediment or brown "growth," but simply clear water, and in which the Pelomyxas did not. increase in number, the irregular, branched condition (Figs. 6 and 7) was extremely common. In these dishes it is evident that food was scarce from the start, and the peculiar shape of the Pelomyxas is prob

curves and complexly branched, Remaining pseudopodia project Zeiss A × 2. Reduced to 1⁄2. curves, lying in planes nearly at

FIG. 6.-P. car, as an opaque object. Body thrown into bold resting on bottom (indicated by lines) at four points. freely into water. One millimetre drawn to same scale. FIG. 7.-P. car, as an opaque object. Body thrown into two right angles with each other. Body rests on bottom (indicated by lines) at four points, one pseudopodium projecting freely upwards. Zeiss A × 2.

Reduced to 1⁄2.

of the animals as thrusting their substance out in all directions of space, searching for food.

When brought on a slide in a drop of water, these animals assume the general shape of Amaba proteus. The body expands in a horizontal plane, and is, as a whole, applied to the surface over which it is creeping (Fig. 8). This is the case whether the drop be uncovered or covered cover was always supported with wax feet, so as to permit free movement. This flattened shape is not directly caused by confinement between two surfaces (surface film and slide, or cover and slide), because it is also usually assumed when the Pelomyxa is first placed in

a watch glass with plenty of water. It would appear to be the shape into which the amoeboid body, more or less contracted after the reception of a

shock, normally expands, before assuming any more characteristic habitus. If the Pelomyxa, owing to the shock of having been transferred to the watch glass, has contracted into a very compact shape, it may (rare condition) throw out short radial pseudopodia all over its body, excepting the lower surface (applied to the glass), Fig. 9. This condition is transitory, soon passing into the stage shown in Fig. 8.

FIG. 8.-P. car. moving freely, on slide, under supported cover. Arrows indicate direction of endosarcal currents. Longitudinal, and papillose wrinkling at the ends of pseudopodia, out of which current is flowing. Only the most conspicuous vacuoles, nuclei, and albuminous globules represented. Zeiss A X 2. Reduced to 3.

Size. In the relatively contracted shapes (Figs. 8 and 9) P. carolinensis measures about I mm. in diameter. The largest form actually measured, in which the body was of the slender irregular character shown in Figs. 6 and 7, measured in a straight line from pseudopodium tip to pseudopodium tip 2.8 mm. Some two hundred specimens of this species were examined by myself and the class demonstrator during September; and for the elongated shapes, the length may be said to vary from 1 to nearly 3 mm., the common length being 1.5 mm. to 2 mm. These measurements may

FIG. 9.-P. car. as an opaque object. Shortly after having been transferred to watch glass. Body covered with short radial pseudopods. Zeiss a, × 4. Reduced to 3.

be taken as characteristic of the adult condition, since the Pelomyxas were always picked out with the unaided eye, no effort being made to discover young forms with the microscope.

Structure of the Body. There is a perfectly clear peripheral (ectosarcal) region, which in the living state is very narrow, being conspicuous only at the ends of expanding pseudopodia (Fig. 8). The granular, more opaque and fluid endosarc contains numerous nuclei, vacuoles, and other bodies. Though the endosarc is naturally lighter near the edge than further in, this difference in transparency is due to a difference in thickness and not to a difference in composition. The nuclei are very abundant, and scattered without order through the endosarc. They are elliptical in shape, and measure 18 μ x 16μ (typical case). The vacuoles in the endosarc vary greatly in size. Large ones, distinct with an a2 (Zeiss) objective, and often measuring 40 μ in diameter, are scattered about in some abundance. When the body is compressed, or when sections are examined, the endosarc is seen to be honeycombed with vacuoles of all sizes; the very small ones, a few microns in diameter, being especially abundant. So abundant are the vacuoles in parts of the endosarc that the optical effect (in section or thinly expanded pseudopodium) is that of a spongy reticulum.

There is no contractile vacuole in this form. If a vacuole disappears, it does so simply because of the shifting of the protoplasm. The endosarc contains in the greatest abundance minute crystals, which contribute very materially to its dark appearance with transmitted light. These bodies are of an elongated fusiform shape, about 2 in length. When seen end on, they look like dots. They are readily soluble in alcohol and in dilute acetic (used in acetic carmine and methylgreen solution), but are neither stained nor dissolved by one per cent osmic. Their diminution in size and gradual disappearance, when treated with the above solvents, may be watched under the microscope. It requires but a few minutes for them to vanish completely, leaving the other inclusions much more distinct than they formerly were.

Scattered abundantly through the endosarc are spherical bodies, having in the living animal a bright appearance with a dark contour, and looking much like oil drops. They very commonly have a diameter of about 8 microns, though smaller ones of all sizes are present. These bodies evidently correspond to the "Glanzkörper" originally described by Greef1 in P. palustris, although in the latter form they may reach a much larger size than I have observed in P. carolinensis. These "refringent bodies," as Gould 2 calls them, are insoluble in alcohol. They are stained by osmic acid and by iodine (alcoholic solution), in nowise differently from the granules of the endosarc (i.e., are browned). They cannot, therefore, be of a fatty or starchy nature. The contents of the bodies is fluid, as may be demonstrated by allowing the Pelomyxas to be gradually compressed through the slow evaporation of water from under the cover-glass. At a time when the arrangement of the coarser and finer granules of the protoplasm is not interfered with, the globules burst and run together, suggesting fat droplets very strongly, but even in this condition osmic acid does not blacken them. On the other hand, the globules are stained a deep blue with hematoxylin. In sections (fixed in Zacharias, stained with Delafield's hæmatoxylin) it may be seen that the endosarc is thickly studded with coarse granules, which stain blue with hematoxylin. The smallest refringent bodies, recognizable as such, differ but little in appearance from these coarse granules. They are slightly larger, of a more rounded shape, and take a deeper stain. From these minute globules, all gradations in size may be found up to the large ones, 8 microns in diameter. With the increase in size the depth of coloration increases an effect due doubtless to the greater diameter. The bodies, when stained with hæmatoxylin, present a perfectly homogeneous appearance. From the evidence at hand, it would seem to me that the bodies are globules of an albuminous nature, consisting of a pellicle, enclosing a more fluid substance. Greef (loc. cit.) inclined to the

1 Arch. f. mikr. Anat., Bd. x, 1874.

2 Notes on the Minute Structure of Pelomyxa palustris, Quart. Journ. Micr. Sci., vol. xxxvi, 1894.

belief that the "Glanzkörper" were of intranuclear origin, and were concerned in reproduction. Gould (loc. cit.), working on P. palustris, failed to see evidence for the truth of these ideas, and in the form which I have studied there was no such evidence. Gould found the "Glanzkörper" to have a homogeneous appearance when stained with ordinary stains (the exception does not seem to have any special significance); and she reached the conclusion that they were "almost certainly either solid structures

or filled with coagulable

fluid." With the latter alternative I agree.

The condition of the albuminous globules in starved individuals deserves a word. In healthy, active specimens the globules are scattered all through the In certain inendosarc. dividuals kept without food in pure water for several weeks, the globules were much more numerous than in normal specimens, and were aggregated together in several regions of the body. In each such region (Fig. 10) the globules were thickly crowded, while elsewhere they were nearly absent. These starved Pelomyxas were about one-third the common size of healthy specimens, and were exceedingly sluggish in movement.

dissolved out with alcohol. Zeiss D x 4. Reduced to 3.

In specimens of Pelomyxa kept without food for some time. the body contains no inclusions except such (granules, crystals, albuminous globules) as seem to be normal and constant constituents. Owing to its large size and freedom from foreign inclusions, P. carolinensis presents certain marked advantages for the study of the fundamental structure of protoplasm. As a living object it is perhaps no better than smaller rhizopods, though under a cover-glass the pseudopodia may flatten out into very thin sheets. On the other hand, it is easy to handle for sections, and in sections the vacuolar walls in particular are instructive. One of the large vacuoles may be cut into several sections, and will thus afford both true sectional and surface