INTERACTIONS OF PROTOPLASMIC MASSES. I x> 



near an Arcella the two bodies did not attract eachother. This 

 \\.is done on ten different occasions; each time the fragment w.i- 

 placed within loomicra of the organism, but neither body -ho\\v<l 

 any response to the other's presence. Chance wandering -h<>uld 

 have brought the two masses together in a certain percentage of 

 es. This did happen on two occasions out of the ten tried, 

 but nothing resulted from the contact. In both instances the 

 animal moved on as if the fragment had been merely a mechanical 

 obstruction. 



Another observation which is probably worthy of mention in 

 this connection, is that under ordinary circumstances two A rcella-, 

 \\hich would re-act negatively towards each other's fragments, 

 may come in contact with each other's pseudopods without 

 causing any disturbance; but when a protoplasmic fragment of 

 one of these organisms is in their midst, it was frequently observed 

 that their pseudopods would be shattered upon making contact. 



With these various facts established, it seems evident that the 

 inability of an organism to fuse with a pseudopodial fragment is 

 due to a difference in the physiological constitution of the pro- 

 toplasm involved. It is generally considered that morphological 

 dillerences are merely physical expressions of physiological 

 changes a kind of cause and effect relationship. If this be true, 

 then physiological tests offer finer distinctions between minute 

 variations than can be jxrceived in the structure of organisms. 

 Furthermore, as shown by the experiments in which one line of a 

 cl.me was placed in a culture medium containing I per cent, su- 



-e, physiological changes may persist for a long time ai 

 morphological differences have disappeared. 



Most investigators in the past have, of necessity, studied 

 \.iriations among protozoa by making use of structural differ- 

 ences. While these arc undoubtedly of great importance, they 

 d<> not offer as delicate a method of determining variation-, or as 

 -ure a means of detecting them. Anyone who ha- oli-i-r\ed a 

 "-hattering" reaction can but be impressed with tin- fa< t that a 

 marked difference exists between the reacting ma-ses a few 

 generations back they were parts of the -ame individual; t hex- 

 have diverged by means of binary ti--ion until they not only fail 

 to unite when brought together, but are shattered into in. my 

 pieces. Why does this happen? We can postulate many pos>il>le. 



