CYTOLOGY OF THE MYXOMYCETES. 77 



visible organization, are, I believe, without counterpart in any 

 other living organisms, outside the Myxomycetes. We must 

 not commit the usual error, however, of calling this protoplasm 

 homogeneous, because homogeneous protoplasm would be in- 

 capable of any vital manifestations or of activity of any sort. 

 They stain light gray with iron hematoxylin, green with fuchsin 

 methyl green, yellow with the Altmann method, and a dull pink 

 by the Benda .method. Around their margins groups of nuclei 

 with a few mitochondria may be seen and a greater tendency 

 toward vacuolation is noted. 



In other parts of the plasmodium the mitochondria are fairly 

 abundant (Fig. 5). They are for the most part spherical and of 

 quite uniform size, varying between 0.25 and o.5/x in diameter. 

 The absence of the really tiny mitochondria, to be seen occasion- 

 ally in higher forms, should be noted. Since the mitochondria 

 never exceed these limits, the possibility of plast formation may 

 be definitely excluded, except perhaps along the margins of the 

 capillitial vacuoles. Rod-like mitochondria occur but they are 

 quite rare. Filamentous, net-Jike and ring forms were never 

 seen. The spherical mitochondria often clump together in pairs 

 like diplococci or in linear series like streptococci. There can be 

 no confusion with bacteria, however, because of their perfectly 

 definite and characteristic reactions to fixatives and stains, which 

 have already been mentioned. They are likewise spherical and 

 look quite homogeneous. They stain quite darkly with iron 

 hematoxylin and undergo definite modifications with the ap- 

 proach of spore formation, to be described subsequently. The 

 ground substance is but faintly vacuolated and the nuclei are 

 scattered irregularly, but fairly evenly. 



Sometimes the vacuolation of the ground substance is much 

 more marked, as is illustrated in Fig. 3. The vacuoles them- 

 selves are quite large and are usually, though not always, spheri- 

 cal. They often seem to run together. They contain for the 

 most part a colorless liquid, never distinct spherules of protein as 

 in the so-called "vacuoles de segregation" of Renaut and Du- 

 breuil. Their walls are merely separation membranes and can- 

 not be distinguished except in Cribraria where well formed and 

 quite thick boundaries occur. 



