MYCETOZOAj LABYRINTHULIDA. 43 



From the foregoing brief recapitulation of the developmental history of 

 this group it is evident, however, that we have here a quiescent or resting 

 phase preceding sporular reproduction corresponding on a compound and 

 enlarged scale with the simple encapsuled or sporocyst state of the more 

 ordinary Protozoa known as encystment. In both the formation of the 

 gigantic compound plasmodium and in the development therefrom of the 

 characteristic sporangia, these Myxomycetes exhibit certain phenomena 

 singularly suggestive of a more or less remote affinity with the sponges. 

 In these latter also the initial term takes the form of spore-developed 

 uniflagellate monads, which, uniting in social colonies, form a gelatinous 

 mass corresponding closely with the plasmodial element of the former 

 group. In the fine horny network usually contained with the spores within 

 the sporangium developed by the mature plasmodium, a substance is pro- 

 duced singularly resembling the fine horn-like elements or keratose fibre of 

 certain sponges, while, what is still more remarkable, in certain forms 

 spicule-like bodies composed of carbonate of lime are also developed within 

 the substance of the walls of the sporangium, or so-called " peridium," that 

 accord substantially in outline with the stellate siliceous spicula of the 

 Tetthyidae and other familiar sponge-groups. In illustration of the apparent 

 close approximation of the Mycetozoa to the Spongida and other flagellate 

 Protozoa, as here presumed, the lower half of Plate XI. of this volume, 

 with its accompanying descriptions, has been devoted to a reproduction of 

 some of the more characteristic figures given by de Bary and Cienkowski 

 in the works quoted, that would appear to substantially support the 

 author's views. 



Two or three orders of the Protozoa, included within the section of 

 the Pantostomata and indicating apparently an independent derivation 

 from the central ancestral stock, have yet to be mentioned. That of the 

 Labyrinthulida, as- typified in Cienkowski's genus Labyrinthula, exhibits in 

 its normal and adult condition a more or less extensively ramified or reticu- 

 late sarcode expansion upon submerged objects, corresponding to a consi- 

 derable degree with the finely branched plasmodia of certain of the 

 Myxomycetes last described. This expansion, however, does not appear to 

 be derived from, or to be associated at any date of its existence with flagel- 

 liferous zooids, while an additional element in the form of minute ovate 

 or spindle-shaped bodies, travelling in the directions assumed by the 

 characteristic currents of circulation or cyclosis, is to be observed. In this 

 last-named feature the constituent sarcode exhibits a close correspondence 

 with that of the test-inhabiting Foraminifera, and the natural position of 

 the group, as indicated in the diagram, would appear to be midway between 

 the latter order and that of the Myxomycetes. The derivation of the 

 Foraminifera themselves from the Amcebina, through such types zsArcella, 

 Lieberkuhnia, and Gromia, is too patent to require prolonged notice. Of the 

 small supplementary group of the Gregarinidae, it remains to be remarked 

 that it exhibits a similar type of degradation or retrograde development in 



