6O THE CELL. 



rod-shaped structures to which he has given the name "thread- 

 granules" or mitochondria. The mitochondria can be differentially 

 stained and are not distributed irregularly through the cell proto- 

 plasm, but in certain definite regions. They are regarded as in part 

 identical with the microsomes. This thread-like substance is known 

 as protoplasm in the stricter sense (Kupffer, 75); also as spongio- 

 plasm, or the fibrillar mass of Flemming (82). The other constit- 

 uent of the cytoplasm is a more fluid substance lying between the 

 threads in the meshes of the spongioplastic network, and is known 

 as paraplasm (Kupffer), hyaloplasm, cytolymph, or the interfibrillar 

 substance of Flemming. According to most investigators, the 

 more important vital processes of the cell are to be identified with 

 the spongioplasm, and are controlled by the nucleus, while the para- 

 plasm assumes an inferior or passive role. With special methods 

 Altman (94) was able to demonstrate granules in the protoplasm, 

 associated with, but not in the spongioplastic threads. To these he 

 gave the name bioblasts, and referred the vital qualities of the proto- 

 plasm to them. Butschli believes the protoplasm to consist of 



_ Cilia. 



Fig. II. Cylindric ciliated cells from the primitive kidney of Petromyton plancri : 



X 1 200. 



separate, honeycomb-like spaces, which give it a foam-like structure 

 foam-structure of protoplasm. 



Protoplasm displays phenomena of motion, shown on the one 

 hand by contraction, and on the other by the formation of processes 

 that take the form either of blunt projections or lobes, or of long, 

 pointed, and even branched threads or processes known as pseudo- 

 podia. The extension and withdrawal of the pseudopodia enable the 

 cell to change its position. The point of such a process fastens to 

 some object and the rest of the cell is drawn forward, thus giving the 

 cell a creeping motion wandering' cells. Certain cells take up and 

 surround foreign bodies by means of their pseudopodia. If these 

 bodies are suitable for nutrition, they are assimilated ; if not, they 

 can, under certain circumstances, be deposited by the cell- in cer- 

 tain localities (Metschnikoff 's phagocytes). Similar thread-like 

 processes which, however, can not be drawn into the cell, occur in 

 some cells in the shape of cilia, which are in constant and energetic 

 motion ciliated cells. Certain cells possess only a single long pro- 

 cess, by means of which unattached cells are capable of direct or 

 rotating motion -flagellate cells, spermatozoa. 



