P LAS MODI A OF &THALIUM 115 



up to them. Unfortunately no such spot is present on Photo- 

 graph XVII. , but nevertheless the radiate layer of alveoli is quite 

 recognisable as a clear border to some gaps. 



The plasmodium further shows us with particular distinct- 

 ness the frequent transition from the usual honeycombed into 

 the fibrous structure. Wherever strands of protoplasm are 

 stretched across like bridges between neighbouring branches 

 that is to say, in general wherever the protoplasm is subjected 

 to a strain or tension, the structure appears fibrillar-alveolar, the 

 direction of the fibres running constantly in the direction of the 

 tension, and hence in bridges, for example, always parallel to 

 their long axis. In such fibrillar bridges and strands the radiate 

 alveolar layer can also be always plainly traced at the surface. 



Bridges of this kind are often so attenuated in the middle 

 that they consist of only a single series of alveoli, and at last, 

 indeed, nothing more is to be seen of any structure, and they 

 resemble the very fine pseudopodia described already in the 

 Rhizopoda. 



At the end of the plasmodial network which is occupied in 

 creeping forwards, protoplasm quite hyaline in appearance and 

 free from enclosures is usually to be observed during life. It 

 can easily be established that here we are not dealing with a 

 very thin and hence apparently structureless layer. This 

 hyaline protoplasm at the anterior end is, on the contrary, for 

 the most part very thick, and corresponds to the homogeneous 

 border at the anterior end of Amcebce. After fixation it proves, 

 in like manner, to be distinctly and finely alveolar, and at times 

 also finely radially striated : the layer of radiate alveoli can also 

 be plainly recognised at its surface. I will, however, return again 

 below to the question of the reality of its structure. 



Fine plasmodia dried up on the slide in the air still show the 

 honeycombed structure distinctly in thin places when examined 

 in air ; with a higher focus also the image of the false network 

 can be made out beautifully. I set especial value upon this 

 observation, as I have already pointed out before (1890) for the 

 similar case of Bacteria. For since after drying up there can 

 certainly be no question of coagulation or precipitations, the 

 visibility of the structure in desiccated protoplasm may be taken 

 as a definite indication that it must also be present in the living 

 condition, and is not a product of the media of fixation. 



I have made use of such dried plasmodia for deciding a 

 further question, which is especially important. It is well known 

 that there is as yet a lack of any sure proof as to the nature of 

 the contents of the protoplasmic alveoli, although in my idea 

 everything is in favour of its being a watery solution. Now if 



