Knowledge of the Avacehx. 113 



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 dis- 

 tinctly to be seen. 



Auerbach had also observed this liquefaction into a disk, as 

 is shown by his fig. 8 ; but he conceived of it as a phenome- 

 non of expansion in which the cell-membrane also had to take 

 part ; but we now know that no such membrane exists, and 

 that the envelope is to be regarded only as a transitory con- 

 centration of the outermost layer of sarcode, and can at any 

 time dissolve again (see fig. 11). 



Taking into consideration some other forms belonging here, 

 Amoeba bilimbosa of Auerbach is the first to be mentioned. I 

 do not think that it is identical with those just described ; the 

 very distinct figures given by the discoverer (plate xix.), the 

 difference of size, and several other differences are opposed to 

 such a notion. In this case nothing is said of a disappearance 

 of the cortex ; and this reminds us more of the conditions 

 stated by Greeff" {he. cit.) to occur in his Ampliizoaella 

 digitata (fig. 18). 



Special interest also attaches to Coddiojpodlum pellucidum 

 of Hertwig and Lesser *, which so closely resembles A. acti- 

 iioi^liova that, as already stated, its discoverers regarded it as 

 identical with the latter. But if the description of Hertwig 

 and Lesser is correct (and this can hardly be doubted in the 

 case of such accurate observers), there can be no further 

 question of a union of the two species. Thus the envelope of 

 Cochliopodium represents a true carapace, which " shows a 

 hatching perpendicular to the surface," and thus acquires a 

 great resemblance to the carapace of an Arcella. From its 

 firmness it cannot be perforated by pseudopodia, and it has 

 only a wide aperture " opposite the cell-nucleus " for the issue 

 of protoplasmic processes, which gives it perfectly the ap- 

 pearance of a monothalamian when it is looked at from the 

 side (Taf. ii. fig. vii. A). In this position Cochliojyodiam 

 would then correspond to ray figure 9. But, singularly enough, 

 a state also occurs, and is very distinctly figured by Hertwig 

 and Lesser in their fig. vii. C, which exactly represents an 

 Amoeba aciinopliora when the cortical layer has liquefied on 

 all sides (fig. 12). 



Hertwig and Lesser explain the matter by supposing that 

 the perfect disappearance of the envelope is only delusive, 

 owing to the animal here being seen not from the side, but 



* Log. cit. pi. ii. tigs. 7, 8. 



