AMON& SIMPLE .SA.UCODE OB&AJTISMS. 



267 



green, the whole, or part, of tlie surface is seen to be in most 

 cases covered with fine villi-like processes, a condition very similar 

 to one which has been frequently described as occurring in 

 Amoeha, 



Towards the centre of the protoplasm were numerous pellets 

 composed of foreign matter, evidently the remains of nutriment 

 derived from plants and ingested as in other amoeboid or- 

 ganisms. 



Ryalodiscus rubicundus (fig. 2) is another form described by 

 Hertwig and Lesser. It differs from all known sarcode animals in 

 its peculiar mode of locomotion ; for while, in all other Rhizopoda, 

 locomotion is effected by variously formed pseudopodia, by which 

 the organism is pushed or pulled forwards, or by means of an appa- 

 rent pouring forth of a stream of protoplasm, by which it, as it 

 were, flows over the subjacent objects, in Hyalodiscus all parts 

 of the surface contribute equally to the locomotion, and it is only 

 the direction in which all the individual parts of the surface move 

 that determines the line in which the organism glides forwards. 



Fig. 2. 



Hyalodiscus rubicundus. The animal in the act of creeping, viewed laterallj'. 

 ( After Hertwig and Lesser.) 



The form of Hyalodiscus rubicundus is that of a disk flattened 

 on one side, convex on the opposite. Its body consists of a homo- 

 geneous, colourless, and hyaline external layer (ectosarc), and a 

 granular central mass (endosarc), which is loaded with brownish 

 red corpuscles. In the middle of the endosarc is a nucleus, and 

 towards its periphery numerous vacuoles ; but whether these are 

 or are not contractile could not be determined. 



Though the Hyalodiscus moves with considerable velocity over 

 the stage of the microscope, scarcely any change of shape can be ob- 

 served in it — a feature in which it strongly contrasts with the pro- 

 tean changes of an Amoeba. During the progression of Hyalodiscus 



