STRUCTURE OF PROTOPLASM. 309 



logical and botanical workers are the ova of marine organisms, 

 although the myxomycetes are in some respects still better, for 

 we have in them the largest masses of pure protoplasm known. 

 The observations here published were made upon myxomy- 

 cetes, pollen-tubes, the oogonia, ova, and embryos of Fucus, and 

 the ova of Echinarachnius . 



OBSERVATIONS. 



MYXOMYCETES. 



Plasmodia of Ceratiomyxa, Badhamia, Arcyria, Cribraria and 

 Fuligo were studied. 



The protoplasmic density of myxomycetes is such that a needle 

 traverses the plasma as through water, although it exhibits a 

 slightly viscid property, for inclusions are pushed ahead of and 

 to the side of a needle before they actually come in contact with 

 it. However, if the point of a needle is broken off, making of it 

 a minute pipette, cytoplasm and small inclusions rush into the 

 opening with great rapidity and from quite a distance. 



The vegetative plasmodium of a myxomycete is of very liquid 

 consistency and remains so no matter how thin the film or fila- 

 ment of streaming plasma may be. If the plasmodium is not 

 active a film or isolated globule of its protoplasm gels very rapidly. 

 The consistency becomes so dense that a moving needle leaves a 

 permanent furrow. 



The old appellation "naked protoplasm," much used in refer- 

 ence to the slime-moulds, is in important respects a misleading 

 one. The surface layer of a plasmodium is a definite morpho- 

 logical structure. The membrane is very extensile, slowly con- 

 tractile, and surprisingly tenacious for so delicate a layer. This 

 superficial layer can be isolated and held by one needle while 

 stretched to several times its length by the other. 



Within the plasmodium are definitely bounded smaller masses 

 of protoplasm, which are apparently normal and in every respect 

 identical with the surrounding plasma bulk. The origin of these 

 smaller included protoplasmic masses was not observed, but their 

 presence is common and they are readily distinguished from oil 

 or other liquid inclusions. Several of these globules were isolated 

 and dissected. Their limiting membrane is exceedingly sensitive, 



