208 Proceedings of the Uoyal Physical Society, 



protoplasm. There is little doubt that a similar structure 

 exists in the vegetable cell, although there the frequently 

 enormous development of sap vacuoles presses the proto- 

 plasm into threads, as in Spirogyra, which cannot be 

 fairly compared to a stroma. There is considerable evidence 

 for believing that in muscle the fibrils represent the stroma ; 

 and Professor Haycraft * suggests that the pseudopodia 

 amosboid cells are mere outflows of semi-fluid protoplasm, 

 squeezed from between the meshes of the stroma by its con- 

 traction, the subsequent retraction of the pseudopodia being 

 accounted for by the relaxation of the stroma, the viscosity 

 of the interstromal matter, and surface tension. While no 

 one who has observed the wonderful activity and the varied 

 forms of pseudopodia emitted by many Protozoan forms 

 (some amo?bie having two distinct forms of pseudopodium,-f- 

 and some protruding cup-shaped processes :|:), or by the cor- 

 puscles of many invertebrates, particularly when uniting into 

 a common amceboid mass,§ will accept the above as a satis- 

 factory explanation; it is, of course, by no means impos- 

 sible that we have here one of the factors of the process ; nor 

 indeed does Dr Haycraft demand much more. 



7. The transformation of ciliated or flagellate cells into 

 the amceboid state has been long known among such organ- 

 isms as Protomyxa, Monads, etc. ; and Huxley II has insisted 

 on the importance of the alternation between these forms, 

 which he terms mastigopod and myxopod, in the morphology 

 of the Protozoa. 



(May not the Mctstigamoeha of Schultze and the similar 

 organisms figured by Butschli and Savile Kent II — which are 

 possessed of both pseudopodia and flagella — be simply forms 

 of mastigopod, sketched during their assumption of the 

 myxopod state ?) 



* Proc. Roy. Soc. Edin., 20tli Dec. 1880. 



t Korotneff, Arch. d. Zool,, Exp., 1878. 



X (Flakojms). 



§ Geddes, "Sur le Fliiide Perivisceral des Oursins " (Arch. d. Zool., Exp. 

 VIII.); and "On tLe so-called Coagulation of Invertebrate Corpiisculate 

 Fluids" (Proc. Hoy. Soc. Lond., 1880). 



II Huxley, "Anatomy of Invcrtcbratcd Animals," 1877. 



•[ ]\Ianual of the Infusoria, Loudon, 1881. 



