2 
BULLETIN OF THE BUREAU OF FISHERIES 
ectoplasmic layer can be distinguished, and there are usually no distinct vacuoles, 
although a few small fat globules are sometimes present. Treatment with iodine 
has failed to disclose any evidence of the presence of glycogen at this stage. No 
trace of ingested food particles could be found, and it is probable that the amebae 
are entirely dependent on liquid food. Although somewhat irregular in shape, no 
ameboid movements could be distinguished, and it seems probable that even when 
in the stomach such movements are comparatively slow. 
The appearance of the trophozoites after being stained is shown in Figures 1 
to 12. They vary greatly in size, and although the majority have a diameter of 
about 10 to 15 microns, individuals with diameters of 20 to 25 microns are found 
occasionally. Usually there is only one nucleus, although multinucleate stages 
occur and are sometimes quite numerous. The latter are, of course, larger than the 
mononucleate amebse and may contain from 2 to 10 nuclei— possibly even more, 
since it is very difficult to distinguish the individual nuclei when crowded closely 
together. However, individuals with 6 or more nuclei are very exceptional and 
can not be considered typical of the species. As a matter of fact, it is believed that 
this ameba must be looked upon as primarily mononucleate, with the occasional 
occurrence of multinucleate forms. 
The nuclei are of the vesicular type and never possess a karyosome, the interior 
being filled with achromatic material that exhibits no distinct structure. The 
chromatin is confined to the periphery of the nucleus, where it sometimes forms a 
thin, nearly continuous layer attached to the nuclear membrane (figs. 1 and 2) , but 
which in many instances can be seen to be composed of a large number of small 
granules (fig. 9). A similar arrangement of the chromatin has been described by 
several writers in other species of amebse. Frequently, instead of forming a more 
or less continuous layer, the chromatin is concentrated in several large masses, as 
shown in Figures 3, 10, and 11. These blobs of chromatin are evidently formed by 
the aggregation of the granules previously referred to, and this is believed to form 
the first stage in the development of the cysts that will be described later. 
The cytoplasm usually has a quite uniform, indistinctly vacuolated structure. 
Occasionally one or more large vacuoles can be distinguished (fig. 9), which in life 
probably contained fat globules, but such vacuoles are exceptional and in nowise 
characteristic. Usually a small percentage of the amebae contain numerous chroma- 
toidal bodies, as shown in Figures 2 and 13. These bodies usually are spherical, 
sometimes somewhat irregular in shape, and vary greatly in size. They are dis- 
tributed uniformly throughout the cytoplasm and apparently have no relation to 
the nucleus. That the presence of these bodies is not due to differences in fixation 
or staining is shown by the fact that amebae containing them are found side by side 
with individuals in which no trace of such structures can be found. It is believed 
that these bodies probably are composed of reserve food material, and it is an inter- 
esting fact that the protoplasm of amebae containing chromatoidal bodies always 
has a dense homogeneous structure without any trace of vacuoles or a network. 
Nuclear division in the ameboid stages is probably always amitotic, as is strongly 
suggested by Figures 4 to 8, which are by no means exceptional. In Figure 12, 
which is drawn from a section through a multinucleate individual, two of the nuclei 
