288 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



ent but homoiogenous individuals touched each other, the pseudopods, instead 

 of coalescing, contracted and disintegrated into small balls, which could be 

 taken into the body of the individual from which they were derived. These 

 observations were made primarily on pseudopods which were still connected 

 with the body of the rhizopod. But even pseudopods which had been cut off 

 from the main body behaved in principle in the same manner; they readily 

 coalesced only with the pseudopods derived from the same individual. If, on 

 the other hand, a cut-off pseudopod was first allowed to degenerate and then 

 to come in contact with another individual of the same species, it could be 

 eaten by the latter. This observation suggests that during the process of 

 degeneration the protoplasm loses its individuality differential and becomes 

 converted into inert material that may serve as foodstuff. 



If we bring into contact with each other, instead of autogenous or homoiog- 

 enous parts, pieces belonging to different species of polythalamous rhizopods, 

 the initial reaction of repulsion, which characterizes homoiogenous contacts, 

 is lacking. Such pseudopods behave to each other in the beginning as they 

 would to foreign material, such as various foodstuffs, with which they first 

 agglutinate and which they then incorporate into their body. But in the case 

 of heterogenous contacts this initial agglutination reaction is followed soon 

 afterwards by a contraction similar to that observed when two protoplasmic 

 particles of homoiogenous origin come into contact, and a secondary separa- 

 tion of the two strange pseudopods takes place. The response to heterogenous 

 protoplasm represents, therefore, a combination of the reactions which take 

 place against a foreign body and of those that occur in contact with homoiog- 

 enous protoplasm. But in addition there may be an effect which suggests the 

 action of a toxic substance; for instance, in some cases if a rhizopod touches 

 the pseudopod of a foraminifera belonging to a different species, the rhizopod 

 may be paralyzed and drawn into the body of the latter organism, although 

 it may subsequently be able to free itself again. 



It is furthermore of great interest that, to judge from the data available 

 regarding Orbitholites, the reactions of nearly related, syngenesious organ- 

 isms towards each other may be like those of autogenous parts of a single 

 individual. Thus different individuals may fuse and form a colony. Jensen 

 considered the early age of the individuals which unite as the principal factor 

 underlying this reaction, but it seems probable that the close relationship 

 between the organisms and the great similarity of their individuality differen- 

 tials are of greater importance than the age. This interpretation is supported 

 by the observation that also in Arcella syngenesious pieces may behave in 

 a similar way to autogenous parts of an organism. 



In other organisms, such as Difflugia, somewhat related but less sharply 

 differentiated effects are noted. While here, again, two autogenous frag- 

 ments of protoplasm may coalesce, homoiogenous particles as a rule react 

 differently towards each other, although occasionally the homoiogenous and 

 autogenous parts behaved alike. In the case of Arcella polyposa, the more 

 recent experiments of Reynolds confirm the earlier observations, according 

 to which autogenous pseudopods which come in contact with each other 



