Dr. M. Verworn's Biological Studies of Protista. 157 



possible. The protoplasm had protruded somewhat, and it 

 was distinctly observable that the protoplasmic bodies of the 

 two individuals had become fused into one, in such a manner 

 that the hyaline protoplasm with the pseudopodia foi-med a 

 circlet surrounding, like a girdle, the endoplasm, which ex- 

 tended into both the shells. I was then astonished to see 

 that in the endoplasm, besides a dark mass consisting chiefly 

 of sand-grains, there were about thirty or thirty-five nuclei of 

 0-2 millim. in diameter, which presented the ordinary appear- 

 ance of Difflugian nuclei and appeared of a dark red colour. 

 At first I thought that the appearance of these numerous 

 nuclei must be connected with the conjugation-process, until 

 I ascertained from the examination of other individuals, taken 

 from different glasses and at different times, that all the indi- 

 viduals always contained from fifteen to twenty nuclei, and 

 that, consequently, DIfflugiaurceolata is a multinucleated form. 

 One specimen, from which one side of the shell has been sepa- 

 rated under the microscope by means of a very pointed and 

 sharp lancet, is shown in PI. IX. fig. 2. Within the shell will 

 be observed the greyish-brown endoplasm, which owes its cha- 

 racteristic colour to innumerable very small brownish granules 

 with strong refractive power. In it lie the nuclei (the dark 

 spots in the figure), together with nutritive particles, and 

 finally a great number of sand-grains, the latter partly only 

 adherent, but partly also completely immersed in the proto- 

 plasm. In the neighbourhood of the aperture is the hyaline 

 exoplasm, which extends outwards its finger-like pseudopodia. 

 My interest was most excited by the accumulation of sand- 

 grains which occurred in the endoplasm of the Difflugia ; 

 and as I found this to be a pretty regular constituent in the 

 protoplasm of all the specimens examined, I supposed that it 

 was employed in the formation of the shell. Biitschli * has 

 already indicated the probability that " the foreign material 

 applied to the construction of the shell was taken up into the 

 protoplasmic body-mass of the Difflugia itself and subse- 

 quently deposited at the surface for the formation of the shell." 

 Gruber \ adopts Biitschli's suggestion, and with reference to 

 the frequently observed phenomenon that other Rhizopoda 

 take up sand into their protoplasmic body-mass he says : — 

 " Scarcely any doubt will remain that Butschli's opinion with 

 regard to the Difflugian shell is correct, and consequently 

 these animals themselves will select and take up into themselves 



• In Bronn's ' Klasseu und Orduungen des Thierreichs,' Protozoa 

 (1880). 



t " Die Theiluug &c.," he. cit. 



