276 PROTOPLASM 



a whole as long as the surface tension does not come into 

 play. 



The formation of a simple pseudopodium of an Amoeba, 

 Engelmann thinks, can be referred to " a general contraction 

 of all the inotagmas of the portion of the hyaline cortical 

 layer which is bulging forwards." To me, however, the origin 

 and gradual elongation of a larger pseudopodium does not 

 seem to be intelligible in this manner. If we assume that 

 the inotagmas of the hyaline cortical layer are all directed 

 parallel to the surface of the region in question, of the body 

 of the Amoeba, and if we then imagine them contracted to the 

 fullest extent, so that they become greatly thickened in a 

 direction at right angles to the surface,^ there will of course 

 result a thickening of the cortical layer of the portion of the 

 surface in question, which may produce a moderate bulging 

 forward of it, but with that the process will have reached its 

 limit. For since we know that the cause of the elongation 

 of the pseudopodium, and of the current that passes through 

 the protoplasm, has its seat at the tip of the pseudopodium, 

 and that here, at all events, the contraction of the inotagmas 

 reaches its maximum at the commencement, a further con- 

 traction does not seem to be possible at this spot. The 

 theory, therefore, gives indeed an explanation for the first 

 slight bulging forwards, but is not able to explain the 

 further growth of the pseudopodium. For it seems inadmis- 

 sible that the inotagmas in question should continually 

 contract further. If, on the other hand, it was thought 

 necessary to assume in some way that the layer of con- 

 tracted inotagmas at the tip of the pseudopodium finally 

 became ruptured and the protoplasm lying beneath, which 

 had come to the surface, now contracted in its turn, this view 

 would also seem to be inadmissible, quite apart from the 

 improbability of such assumptions, since a rupture will not 

 in any case occur at the spot where contraction is taking 



^ Although Engelmann makes no exact statements with reference to the 

 power possessed by the inotagmas of becoming shortened or thickened, yet it 

 seems to me beyond a doubt, that he must imagine the degree of shortening 

 to be a relatively moderate one, namely, of about the same extent as he has 

 become acquainted with from the shortenings that can be observed in mus- 

 cular contractions. 



