174 THE BEHAVIOR OF IXJWER ORGANISMS. 



extensive paper (1898). My observations show that this transforma- 

 tion is confined within much narrower limits than Rhumbler supposed. 

 In the account which he gives of the movements of Amoeba this trans- 

 formation (the " ento-ectoplasm process," as he calls it) plays a very 

 large part, and is essential to locomotion. At the anterior end, accord- 

 ing to Rhumbler, endosarc constantly flows out to the surface and is 

 there transformed into ectosarc, flowing back as such along the surface 

 of the body. Somewhere in the posterior part of the body or at the base 

 of a pseudopodium this ectosarc passes inward and is retransformed 

 into endosarc. These supposed processes are indicated in the diagrams 

 from Rhumbler, Figs. 30-33. 



My observations show that this view of the constant inter-transforma- 

 tion of the two layers is incorrect, and that we must attribute to the 

 ectosarc a much higher degree of permanence than Rhumbler supposed. 

 There is no regular transformation of endosarc into ectosarc at the 

 anterior end. On the contrary, the ectosarc here retains its continuity 

 unbroken, moving across the anterior end in the same manner as across 

 other parts of the body. In the same way, the ectosarc is not regularly 

 transformed into endosarc in the hinder part of the body. We can trace 

 a single definite point on the ectosarc (or a complex of such points 

 having a definite relation to each other) continually until it has passed 

 completely around the Amoeba ; several complete rotations of this sort 

 are described from actual observation on page 141 . In the species having 

 very changeable forms a single point on the ectosarc may be traced, 

 for example, from the surface of a pseudopodium at the posterior end 

 across the whole length of the body to near the tip of a long pseudo- 

 podium at the anterior end (Fig. 49, p. 155) ; there is no reason to 

 suppose that it could not be traced indefinitely but for the difficulties 

 of observation. 



On the other hand, there is no doubt that ectosarc may be trans- 

 formed into endosarc, and vice versa, under certain conditions. This 

 process was apparently first clearly seen by Wallich (1863, #, p. 370). 

 Wallich saw the formation of " eruptive pseudopodia " by the outflow 

 of the endosarc through a small perforation in the ectosarc. A portion 

 of the latter was thus covered by the endosarc, and gradually resorbed. 

 Rhumbler figures a similar case (1898, p. 152), and I have repeatedly 

 seen such. Further, as Rhumbler has shown, and as I can confirm, in 

 A. verrucosa food bodies are enclosed in a layer of thick ectosarc, which 

 passes with the food into the endosarc, there to be resorbed (see p. 195). 



Thus, it is clear that there may be a transformation of one layer into 

 the other under special cii'cumstances, but such transformation is much 

 less general than Rhumbler supposed, and is by no means a regular 

 accompaniment of locomotion. 



