Dr. M. Vervvorn's Biological Studies of Protista. 161 



exactly the same appearance as immediately after the opera- 

 tion. The cut margins remained just as irregular as on the 

 first day, and although all the individuals had taken up glass- 

 granules, no deposition of them had occurred at the point of 

 lesion. The experiments were afterwards made with other 

 glass-particles and with sand-grains, but no repair or comple- 

 tion of the shell ever occurred. 



Finally, the whole shell was removed from some specimens 

 under a low power, without inflicting any injury upon the 

 protoplasmic body of the Protistan. In this way I obtained 

 perfect Diffiugim without shells, which also behaved quite 

 normally. They took up sand-grains (or glass-particles), 

 crept about with their finger-like pseudopodia, and frequently 

 flattened themselves out, when it was particularly easy to see 

 that the incepted glass-granules formed a small aggregation 

 in the interior of the protoplasm. When only short pseudo- 

 podia were emitted the Protista had a great resemblance to 

 Pelomyxa, which was still further increased by the greyish- 

 brown coloration, the incepted glass-granules, and the great 

 number of nuclei. I succeeded in keeping these shell-less 

 Difflugice alive in the normal state for nearly three weeks 

 without any trace of a regeneration of the shell being observ- 

 able. The surface of the protoplasmic body did not present 

 the least excretion or deposition of solid matter ; it was rather 

 soft, performed Amoeboid movements, and developed pseudo- 

 podia until the last, when the Protista became the victims of 

 an unlucky accident. 



When I consider that I made my experiments at dififerent 

 times upon a very great number of Diffiugice^ that I varied 

 the experiments in every way, and that I carefully observed 

 and examined the individuals operated upon for more than 

 three weeks, I think I may with perfect certainty arrive at 

 the conclusion that the Difilugige do not regenerate the shell 

 when injured or entirely removed. 



POLYSTOMELLA CEISPA, Linn. 



As those forms of Rhizopoda which construct their shell of 

 foreign bodies, such as the Diffiugioij are closely united by a 

 great number of intermediate forms with those which secrete 

 their own shells, such as the Polythalamia, it seemed to me 

 desirable to investigate one of the latter forms with respect 

 to the conditions of regeneration of the shell, and I had 

 afforded to mc an opportunity of doing this in the case of 

 Polystomella crispa^ Linn., from Trieste. These Protista also 



Ann. & Mag, N. Hist. Ser. 6. Vol ii. 11 



