194 Mr. H. J. Carter on the Polytremata. 



when dry may be so termed), which abuts upon the foramina 

 of the walls and, according to Max Schultze as before stated, 

 is divided into chambers which open into each other by two 

 or more stolon-like constrictions, through which these chambers 

 not only communicate with each other but were successively 

 produced, finally opening into the cavernous dilatations which 

 are in direct continuation with the surface through the aper- 

 tures at the ends of the branches ; besides which, accident 

 seems to form openings in the old test here and there, as it 

 does in the chamber of Operculina^ through destruction of the 

 foraminated interspaces, which thus also lead directly into the 

 interior. 



It can now be understood how the spicules and calcareous 

 grains of sand not only find their way into the cavernous dila- 

 tations, and occasionally into the sarcodic chambers them- 

 selves, but also become imbedded in the cancellated structure 

 during its exogenous growth, and thus are found to transfix 

 the test generally, after the same manner as small Foramini- 

 fera were found by Mr. H, B. Brady to have become accidentally 

 imbedded in Loftusia {loc. cit. pp. 749 & 750). 



For want of fit specimens to demonstrate this. Max Schultze 

 was obliged to have recourse to lengthy arguments beginning 

 with the following premises, viz. : — " Either the siliceous spi- 

 cules have penetrated accidentally, or they have been taken 

 in as food, or, lastly, they belong to a parasitic sponge " 

 {loc. cit. p. 416), finally concluding that the presence of the 

 sponge-spicules in Polytrema might be owing to its being 

 infested by a parasitic sponge, and that transition forms be- 

 tween Foraminifera and Porifera have but little probability 

 {lb. p. 417). 



But now that we have " fit specimens," such arguments are 

 not necessary ; for the facts can be told in a few words, viz. 

 that sponge-spicules and minute sand-grains, respectively sili- 

 ceous and calcareous, together with a heterogeneous assemblage 

 of the tests of minute organisms generally, both entire and 

 fragmentary, may be observed to form dried thread-like fila- 

 ments more or less netted together (fig. 6, m m m) , and trace- 

 able into the apertures of the Polytrema (fig. 6, ccc), after 

 which the same kind of material may be found further down 

 in the cavernous dilatations of the test (fig. 6, <?, v v v), leaving 

 no kind of doubt that the dried thread-like filaments were ori- 

 ginally soft pseudopodial extensions of the internal sarcode, 

 which, coming into contact with the minute material mentioned, 

 had thus agglutinated and drawn it into the Folytrema. 



Although the sarcodic substance cannot be well distinguished 

 in these thread-like filaments, it can be seen with an inch 



