Reproductive Processes of Sponges. 379 



forms of the cells to which they belong ; we may also see in 

 the latter their hyaline vesicles with their contained molecules 

 in great commotion, and between the cells themselves the 

 intercellular mucilage (fig. 2 7 f). 



" If this newly formed sponge be torn up, its isolated cells 

 assume their globular or passive form, or become polymor- 

 phous, changing their position and their locality, by emitting 

 expansions similar to the proteans or polymorphic cells deve- 

 loped after a forcible expulsion of the contents of the seed- 

 like body, and differing only from them in being more 

 indolent in their movements " (no. 3, p. 91, pi. iv. fig. 2). 



With this statement, at that comparatively early period, 

 how was it possible to come to any other conclusion than that 

 every part of the sponge-parenchyma is capable of enclosing 

 nutritious material and digesting it like the Amoeba (" pro- 

 tean "), even if we had not had the observations of Lieber- 

 kiihn, confirmed by MetschnikofT (no. 20, p. 374) , to establish 

 the fact ? 



In the first paragraph above quoted I have mentioned the 

 extreme edge of the young Spongilla as composed of semi- 

 transparent substance charged with hyaline vesicles, as if this 

 were a distinct portion ; but from what I have stated at the 

 commencement of this paper respecting the homogeneity of 

 amoeboid cells after amalgamation, defying all attempt to de- 

 tect their individuality, although capable at a moment's notice 

 of separating themselves from each other (as in the conjugation 

 of two Difflugiw) , it is quite possible that this " semitrans- 

 parent substance" may be composed of sponge-cells thus 

 combined, and the " hyaline " their " contracting" vesicles 

 respectively, since, as I have heretofore shown, the ap- 

 parently homogeneous investing membrane or cuticle of the 

 young Spongilla is so composed (no. 6, pp. 24, 25, pi. i. 



Connected with this is the curious fact that the whole of the 

 spongozoa of an ampullaceous sac (" Wimperkorb") may, under 

 isolation, become thus amalgamated, and assume the form and 

 habits of an Amoeba, while the cilia of the spongozoa may be 

 seen still playing in its interior, and the exterior enclosing 

 particles of carmine which come into contact with it (no. 6, 

 p. 26) — finally losing all appearance of cilia internally, and 

 presenting an actinophorous form [ib. p. 33, pi. i. fig. 9). 



Since, then, we find Balfour (no. 19, p. 108) stating, " It 

 has not, so far as I know, been definitely made out where the 

 digestion is carried on. Lieberkuhn would appear to hold 

 the view that the amoeboid lining-cells of the passages are 

 mainly concerned with digestion, while Carter holds that 



27* 



