the Distinctive Characters in ximoeba. 129 



iodine being now applied, the result was similar to that produced 

 in the case of living individuals, — with this exception, that the 

 broken-up masses were not spherical, but irregular and ragged 

 in their outline. 



Here, then, the inference is legitimate, that, whilst vitality and 

 contractility were destroyed by the heat so as to preclude the 

 formation of ectosarc over the torn surfaces, the recession of the 

 granular and other contents towards the centres of the masses 

 yielded unmistakeable evidence that the action was purely che- 

 mical. But still nothing at all resembling membrane was evoked; 

 and the tint imparted externally by the iodine was neither blue 

 nor purple, but brownish; and, as in the case cited by Auerbach, 

 some of the internally contained particles assumed a purple 

 colour. 



In Amoeba, the true ectosarc appears to me to be nothing more 

 than the outer layer of sarcode (for the time being) consolidated 

 by contact with external influences, its depth (or, rather, thick- 

 ness) being dependent on the length of time these influences 

 continue to act upon it without intermission ; whilst the con- 

 solidation referred to is greater at the immediate surface, and 

 gradually diminishes in extent and finally fades away altogether 

 from thence inwards. Leaving just now the question of reci- 

 procal convertibility of ectosarc and endosarc, I would observe 

 that this view is essentially similar to that propounded by Du- 

 jardin. It is corroborated, however, by a fact open to the ob- 

 servation of every one, — namely, that in the nearly quiescent 

 condition of Amoeba, when the outline becomes more or less 

 spherical, the greater amount of consolidation of the exterior 

 layer is shown by the hyaline margin becoming broader, and 

 the whole of the contents being consequently made to recede 

 towards the centre. 



That an increased degree of consolidation does really exist in 

 the outer layer of sarcode, and that the particles of which the 

 entire body is composed are not held together only by the mo- 

 lecular cohesion of which we have examples in the formation of 

 water-globules or oil-globules when placed in fluid media in 

 which they are insoluble, I deduce from this fact, that whereas 

 a foreign body, when of great size and resistent — as, for example, 

 the large Pinnularice so frequently met with in the Hampstead 

 Amoeba, when fresh (Annals, April, pi. 8. fig. 4, and May, 

 pi. 9. figs. 1-8, and in the Actinophrys figured in the number 

 for June, pi. 10. fig. 4) — causes the outer layer to project almost 

 to any extent without rupture (as in the last-named figure), the 

 moment the body is torn asunder by pressure or other violence, 

 such an object instantly slides completely out of the mass, and 

 becomes liberated. 



Ann. ^ Mag. N. Hist. Ser. 3. Vol. xii. 9 



