PEOTOPLASMIC MOVEMENT. 379 



III. The Spontaneous Movements of Protoplasm. 



In accordance with the peculiarities mentioned in the intro- 

 duction, protoplasmic movements in general present a great 

 variety and change in the manner of their appearance, and 

 this is the case to such an extent that it is impossible to give 

 a short description applicable to all cases. Certain definite 

 types may, however, be distinguished, and we may almost limit 

 ourselves to describing these and referring to the fact that 

 they are connected with each other by numerous transitional 

 forms. 



1. Movements of Naked Protoplasm. 



Three chief types may be distinguished, and may be called 

 respectively — Amoeboid movement. Streaming movement, and 

 Gliding movement. 



The amoeboid movement shows itself in the protrusion and 

 retraction of smooth, round, conical, or flattened, at first 

 generally hyaline processes, into which the granular mass from 

 the interior streams in and out.^ The processes may remain 

 separate from one another, or they may ramify and even form 

 networks. In the simplest cases of this kind of movement only 

 slow unimportant changes of the external form of the mass occur, 

 which do not cause a change of position. This is the case 

 with the egg cells of many Vertebrata before fertilization. 

 The phenomena soon become more complicated, as shown in 

 the movements of Amcebse, Myxamcebse, Arcellse, Dif- 

 flugise, many Monads, numerous egg cells (Hydra, 

 Sponges), the white blood-corpuscles of most animals, pus- 

 corpuscles, wandering cells in connective tissue, and many 

 epithelia (frog's cornea), &c. 



We now come to those extensive and often very active 

 streamings which occur in very granular central masses, and 

 those considerable changes of shape which come about 



1 Pirst, and very well described by 0. Fr. Miiller, • Animalcula infusoria, &c.,' 

 p. 10, 178G. 



