222 
T. JEFFERY PARKER. 
three cilia. These latter are of great length, in fact, nearly or 
quite as long as the cells to which they are attached ; in some 
cases, indeed, they are longer. I have never seen anything like 
a collar” at the base of any of the cilia. 
The amoeboid character of the endoderm cells, as seen in sec- 
tions or teased fragments of the living animal, is a well-known 
fact; but the extent and activity of the amoeboid movements 
during life has not been sufficiently insisted on. In sections of 
picric acid or ammonic bichromate specimens, large rounded 
pseudopodia are seen to be given off from the cells into the 
digestive cavity, sometimes to such an extent as completely to 
obliterate the latter. The length of the cells may, therefore, 
vary almost indefinitely ; they may be but little longer than the 
ectoderm cells, or may be two or three times as long. This va- 
riation in the size of the endoderm cells, and the consequent 
variation in the diameter of the digestive cavity, is very marked 
in my series of sections, nearly all of which are taken from large 
specimens,^ killed in a state of half extension. When the endo- 
derm cells are fully extended, it is almost impossible to obtain 
them complete by teasing. They nearly always break across, and 
can only be obtained in a fragmentary condition. 
A very noticeable point about the endoderm cells is the 
presence in their protoplasm, especially towards the far end, of 
dark-coloured irregular granules, of various sizes. It has been 
suggested that these are products of excretion : Kleinenberg 
makes the important observation that their number varies with 
the state of nutrition of the animal. 
I am convinced that these bodies are food particles, taken into 
the protoplasm of the cells, from the partially disintegrated bodies 
of the Entomostraca in the digestive cavity. They are of quite 
the same nature as the contents of the alimentary canal in many 
of the common Cladocera and Copepoda ; they occur chiefly in 
the free end of the cell, and in some cases they have all the ap- 
pearance of being half in and half out of the protoplasm. The 
particles of the more transparent parts of the body of the Crus- 
taceans will naturally not be so evident in the cell protoplasm ; 
even these, however, can be made out in a Hydra in full diges- 
tion, when the endoderm cells of the distal or gastric region are 
completely crammed with transparent sphe^’oids. 
The clearest case of ingestion of solid particles was seen when 
a diatom was seen to be completely imbedded in the protoplasm 
of a cell. 
If this explanation of the dark granules is the correct one 
Hydra \Cill have been shown to exhibit a process- of alimentation 
identical with that described by Metschinkoff in the lower Tur^ 
^ Supplied by Mr, ]3oUon, of Birmingham. 
