4^4 Mr. A. 'J\ Mastermaii on the Xntritive and 



are scattered throughout the mesodermal parts of the colony, at 

 least in Grantia. 



On the other hand, it is possible timt, top^ether witli the 

 morphological differentiation of subdermal cavities, there may 

 be a physiological change of function, and that, as suggested 

 by Sollas (15), the phenomena described by Lendenfeld may 

 be allied to those of inflammation in higher ]\Ietazoa. One 

 may grant that the subdermal amoeboid cells may have a 

 function of ingestion of foreign bodies, without assigning to 

 them the main function of the nutrition of the colony. 



In a later work Lendenfeld (9) comes to the conclusion 

 that carmine is only deposited in the amoeboid cells quite 

 exceptionally, as, for instance, in the case of lesion of the 

 outer layer of cells, and that under normal circumstances it is 

 the choanocytes only which absorb the carmine. 



These statements and results are criticized by Metschnikoff 

 (11), who points out that Lendenfeld grants that fat-globules 

 are taken in by the mesodermal phagocytes ; and he also 

 declares that Lendenfeld's figures give " direct indications of 

 the presence of carmine grains in the amoeboid cells of the 

 mesoderm." 



He remarks also as follows : — " Although it has not so far 

 been definitely ascertained hoic the foreign particles penetrate 

 the mesoderm after they have reached the interior of the sponge, 

 yet it has been clearly shown that they are largely absorbed 

 by the mesodermic cells themselves. . . . Grains have been 

 enclosed by the endodermic cells as well as by tiie amoeboid 

 phagocytes of the mesoderm. 



" In certain sponges there are very few mesodermic cells, 

 which consequently take a small part in englobing foreign 

 bodies ; in others, again, especially in the siliceous kinds, the 

 mesoderm is much better developed, and its more numerous 

 cells can therefore take in a proportionately larger number of 

 these minute ])articles. There arc a few species, such as the 

 iSiphonochalina coriacea, whose mesodermic cells alone enclose 

 all toreign bodies, so that the cylindrical cells of the endo- 

 derm merely serve to keep up the continuous passage of the 

 fluid through the sponge." 



I have attempted to supply the deficiency indicated above 

 by the italicized words of JMetschnikofl', at least for Granda, 

 and I think it most probable that in tlie least differentiated 

 sponges, e. g. Ascetta, we have so-called " endodermic " cells 

 which perform at least two functions, ingestion and digestion, 

 and that they change their form from flagellate to amoeboid 

 according as they j)erform the one function or the other. In 

 the higher diflerentiated sponges the " mesodermic " cells 



