CHOANO-FLAGELLATA; MYCETOZOA. 41 



accompanying diagrammatic plan by the intersection of the circles enclosing 

 the respective groups. A speculation as to the possible affinities of the 

 Tentaculifera in a totally independent direction is recorded in the chapter 

 devoted more especially to the general organization of the Infusoria. 



The line of evolution or phylogeny from the Amcebina to the Dis- 

 costomatous class of the Protozoa, remains to be traced. The direct 

 relationship of the highest and most complex factor in this section, that of the 

 Spongida, to the more simple Choano-Flagellata, as illustrated by the genera 

 Codosiga, Salpingcsca, and other recently discovered types, is, as explained 

 in Chapter V., devoted to the organization of the sponges, too obvious to 

 need extensive comment here. As there demonstrated, the representatives 

 of this last-named organic group can be regarded only as specialized, 

 colonial stocks of similar collar-bearing Flagellata living immersed within 

 a channelled and collectively exuded common gelatinous matrix or cyto- 

 blastema, and whose substance is more usually strengthened by calcareous 

 or siliceous spicula, or a network of horny matter. As demonstrated 

 by the present author in the chapter cited, the separate zooids or units 

 of both the Spongida and simpler Choano-Flagellata exhibit in their 

 developmental phenomena the closest possible affinity. These originate 

 chiefly in either case from mouthless monadiform flagellate germs, thus 

 exhibiting their phylogenetic relationship with thePantostomatous Flagellata, 

 while the adult zooids revert at will to the condition of either Rhizo- 

 Flagellata or simple A mcebcz. In certain species of Salpingcsca, as hereafter 

 described, e. g. 6". ampJwridium, new zooids are shown to originate as 

 amcebiform gemmules separated by division from the parent animalcule, 

 thus completing the retracement of the line to the central or primitive 

 ancestral stock. 



In the foregoing diagrammatic scheme the line of evolution of the 

 Spongida is made to abut upon or traverse the group of the Myxomycetes 

 or Mycetozoa. The reasons for adopting this course require brief explana- 

 tion. Formerly, and by some even yet regarded as a low order of fungi, 

 or as a special group of organisms intermediate between animals and plants, 

 which exhibit at one epoch of their life all the vital characteristics of the 

 former, and at another those of the latter kingdom, their admission into 

 the Protozoic galaxy or system will no doubt encounter objection. The 

 evidence most recently and independently eliminated by L. Cienkowski* and 

 Dr. A. de Bary,t concerning the structure and life-history of this most 

 remarkable group, establishes, however, beyond question their purely 

 animal nature. The Mycetozoa, in common with all ordinary representa- 

 tives of the Protozoa, originate from minute sporuloid bodies which escape 

 from the spore case as monadiform animalcules having a soft, plastic body- 

 substance, a single terminal flagellum, contractile vesicle, and endoplast 



* L. Cienkowski, "Zur Entwickelungsgeschichte der Myxomyceten." Pnngsheim's Jahrbiicher, 

 Bd. iii., Hft. 2 and 3, 1862. 



t A. de Bary, 'Die Mycetozoen. Ein Beitrag zur Kenntniss der Niedersten Organismen.' 

 Leipzig, 1864. 



