REACTIONS OF CELL-BODIES OF DIFFLUGIA. 35 



their cell-bodies. Soon thereafter the masses of severed proto- 

 plasm would bend at the points of contact and the contents would 

 flow up the pseudopods. Jensen (1896) pointed out that in Or- 

 bitolites and Amphistegina chance crossing of pseudopods of dif- 

 ferent specimens may cause instantaneous shattering of the proto- 

 plasm concerned, and that the organisms would occasionally pick 

 up the fragments belonging to themselves and make them again a 

 part of their bodies. He was also able to get the same results by 

 cutting off fragments of pseudopods. Furthermore, he observed 

 that one species would react negatively toward fragments from 

 other species. Later, in 1901, he made some further experiments 

 on Orbitolites in which he obtained practically the same results. 

 In the last paper he indicates that there is some response on- the 

 part of the fragments toward restitution. He calls attention to 

 the fact that tendency toward restitution is stronger just before the 

 severed fragments lose their power of movement. This does not 

 correspond to our findings, and since he does not describe his 

 experiments in detail, it is difficult to know whether or not they 

 have much in common with those made by us. 



There are many unicellular animals that may be cut into two 

 parts and each part display vital phenomena. In the uninucleated 

 forms the part, or parts, lacking a nucleus probably carry on only 

 katabolism or destructive processes. In multinucleated protozoa 

 we often find each mutilated fragment becoming a new indi- 

 vidual — as, for example : when a Stentor, ActinosplicervuM, or 

 Arcella is fragmented. Wilson (1907, '11) separated the cells of 

 a sponge's body and found that these cells would become organized 

 again into a new sponge. But this was restitution through segre- 

 gation and reorganization of parts of a multicellular organism. 

 In Difflugia we have the parts of a cell fusing to retain its former 

 completeness. In this relation it is impressive to observe how 

 definitely ectoplasmic fragments respond, in some cases, to their 

 cell-bodies. As the cell shifts its position the fragment changes 

 its course correspondingly. 



Chemotaxis of some sort is probably involved in the attraction 

 shown between cell-bodies and their fragments, but that point has 

 not been determined. Neither mucous trails nor invisible strands 

 of protoplasm are necessary for the protoplasmic reunion to take 



