212 SUMMARY OF CURRENT RESEARCHES RELATING TO 



liquefied, while on the otlier half the double coutoured enveloping 

 layer is still retained, and on it even two pseudopodial cones with 

 the processes issuing from them are still visible. Fig. 15 is also 

 instructive in another way. There the cortical layer has become 

 fluid, and we see that the two pseudopodia which have persisted, 

 consist of the same hyaline protoplasm as the clear border in which 

 the cortical zone previously sharply sej)arated from it (Fig. 14), has 

 dissolved itself. In the first state, therefore, there would have been 

 an envelope and an endoplasm enclosed by it, and from which the 

 pseudopodia proceeded clearly distinguishable ; in the latter, both have 

 become fused into one. Eapidly as the broad, scarcely visible border 

 had formed, it can just as rapidly contract itself again ; it shrinks 

 to a certain extent together, until the narrow cortical layer again 

 originates from it. 



In this way A. diffluens can continually change its aspect com- 

 pletely in one or other of the modes described. Upon what law this 

 power depends cannot be stated definitely ; very probably, however, 

 different conditions of pressure come into play in the matter. With 

 a centripetal jiressure acting uniformly ujoon the whole periphery, the 

 more fluid parts of the j)rotoplasm are all pressed into the interior, 

 and only the narrow membranaceous boundary remains. This 

 acquires a firmer consistence by contact with the water, and therefore 

 at the points where pseudopodia issue, it is pushed aside by the 

 latter. If the general pressure ceases, the more fluid constituents 

 again come forth from the interior, dissolve the solidified cortical 

 layer, and form the clear border. 



The best illustration of this explanation of the process is furnished 

 by those cases in which a slow flowing forward of the Amoeba in one 

 direction is taking place (Fig. 14). On the advancing side the fluid 

 constituents are pushed on in front ; here all pressure has ceased 

 whilst it acts upon the opposite side, where accordingly the cortical 

 contours are quite distinctly to be seen. 



Auerbach had also observed this liquefaction into a disk as is 

 shown by his Fig. 8, but be conceived of it as a phenomenon of 

 expansion in which the cell-membrane also had to take part, but we 

 know that no such membrane exists, and that the envelope is to be 

 regarded only as a transitory concentration of the outermost layer of 

 sarcode, and can at any time dissolve again (Fig. 11). 



Dealing with Cocldiopodium pelluddum of Hertwig and Lesser, the 

 envelope of which represents a true carapace, the author points out 

 that " a perfecting of this structure may be demonstrated from 

 A. teniaculata through A. adinojiliora to Cochliopodium. It might be 

 conceived that by a further increased tenacity of the cortical zone we 

 shall finally be led to those forms of monothalamous Ehizoi^ods whose 

 envelope forms only a soft membrane closely embracing the sarcode, 

 and which is still so comiiletely at one with the protoplasmic body as 

 to accompany it in all its movements and to be constricted simul- 

 taneously in the division. 



" Glancing back once more upon the phenomena which confront 

 us in the Amcebiform Rhizopods surrounded by a distinct cortical 



