Dr. M. Verworn's Biological Studies of Protista. 159 



then showed that the glass-grains not only remained adherent 

 to the surface of the protoplasm, but were actually drawn 

 into it, so that the interior contained a quantity of blue glass- 

 grains. 



Tlie mode in which the material for the construction of the 

 shell was taken up was therefore ascertained ; but it was some 

 time before I succeeded in discovering individuals engaged in 

 division. I found these in a watch-glass which contained a 

 brood separated from the larger aquarium, but unfortunately 

 only of a few individuals. Nevertheless I had the opportunity 

 of observing different stages of the process of division, and thus 

 of ascertaining that the process is effected in precisely the 

 same way that was accepted by Gruber with regard to the 

 division of Eughjpha, Cyphoderia, &c. First of all there pro- 

 trudes from the sliell-apertures a round, low mound of proto- 

 plasm, which issues further and further, and the convexity of 

 which gradually approaches the spherical form. In one 

 instance its form appeared not to be quite regular, but some- 

 what oblique and impressed on one side. In a further 

 advanced stage the protruded mass of protoplasm had already 

 attained the size of tlie original individual, and I even found 

 a specimen in which it was somewhat larger and broader than 

 the latter. In an individual whose protruded mass had 

 already approximately acquired the size of the old shell, I 

 observed that a ball of glass-granules had already in part 

 entered the newly formed half, in which the protoplasm with the 

 glass-grains showed a slowlyflowing movement (PI. IX. fig. 1). 

 In the most advanced stage of division the protruded protoplasm 

 had already assumed pretty nearly the form of a Difflugian 

 shell of the present species, and the particles of glass had 

 arranged themselves at its surface. The new half seemed 

 not yet to have a solid shell ; but the glass-granules were 

 loosely fitted to one another. On the following day in this 

 specimen the separation of the newly-formed individual was 

 completed, and it was creeping about in the watch-glass with 

 its pseudopodia. Its shell showed the characteristic form, 

 but the pale bluish glass-grains were united to each other by 

 a nearly transparent, but, at any rate, quite colourless con- 

 nective substance, which only some days later began to 

 acquire a darker brownish colour. Together with this speci- 

 men there were on the next day two likewise newly formed 

 individuals which had the same appearance. The other four 

 specimens which I had found engaged in division on the 

 previous day showed scarcely any noticeable alteration since 

 1 had left them, and afterwards it turned out that they were 

 dead. The subsequent attempt at nuclear staining was 



