20 1MUT1SH FRESHWATER RH1ZOPODA. 



seemed evident that by -mechanical irritation a " reflex 

 contraction " of the pseudopodia was produced, and, 

 combined therewith, a secretion of a sticky coat on 

 their surface, which caused the glass granules to 

 adhere to the pseudopodia, and to be drawn in with 

 them. 



Bj r a series of experiments repeated upon other 

 species of Dijfftugia, Verworn ascertained the great 

 regularity of this process. When a Difflugia had 

 extended its pseudopodia to a great length, and was 

 groping about between the glass plates, it was irritated 

 with a sharp needle ; the same effect was then pro- 

 duced with great exactness. The pseudopodia became 

 tubercular, and while previously no glass granules 

 were adherent to them, these now clung firmly, and 

 were slowly drawn into the shell. Specimens, the 

 shells of which were partially removed, showed that the 

 glass grains not only remained adherent to the surface 

 of the protoplasm but were actually drawn into it. 



The same writer had subsequent opportunities of 

 observing individual Difflugiae undergoing division, and 

 found that shell-formation in a young Difflugia accorded 

 exactly with Gruber's observations in the case of 

 Euglypha aheolata. When the protruding mass of 

 protoplasm from the old shell had attained approxi- 

 mately the normal size, he observed that a ball of glass 

 granules had already, in part, entered the newly- 

 formed half, in which the protoplasm with the finely- 

 powdered glass showed a slowly-flowing movement. In 

 a more advanced stage of division the protruded proto- 

 plasm had already assumed pretty nearly the form of 

 the Difllugian shell (D. urceolata], and the particles of 

 glass had arranged themselves upon its surface. The 

 new half seemed not yet to have a solid shell, but the 

 glass granules were loosely fitted to one another. 

 Upon separation from the parent the newly-formed 

 individual was observed groping about in the water, 

 with pseudopodia extended. The shell exhibited the 

 characteristic form, but the pale bluish glass grains 



