144 The Unity of the Organism 



bilitj of naked protoplasm from different organisms — from 

 different individuals of the same and of different species. 



The experiments of H. V. Wilson on the coalescence of 

 dissociated cells of sponges and hydroids particularly, have 

 blazed a seemingly very practicable manipulative path into 

 the subject. Wilson cuts portions of the animals into small 

 pieces, then squeezes these through bolting cloth. This 

 operation separates the tissues into small groups of cells, 

 and to some extent into completely isolated cells. These 

 cells, kept under favorable conditions, soon assemble together 

 into compact masses, and from the masses normal animals 

 frequently develop. Although Wilson has thus far been 

 chiefly occupied with showing that various animals are able 

 within their own species to rehabilitate themselves under 

 such conditions, he has not failed to raise the question of 

 how far coalescence and normal development may take place 

 when tissues of different species are mixed together. His 

 experiments under this head are far less extensive than those 

 on the commingling of cells from different individuals of the 

 same species, but are nevertheless highly instructive. In his 

 paper of 1907 his statement, "Unlike specific substances 

 (protoplasms of quite different species) do not tend to 

 fuse," ^^ is perhaps a somewhat more unqualified denial of 

 the fusibility of the protoplasms of different species ; or 

 stated affirmatively, a somewhat more unqualified assump- 

 tion of the specificity of the protoplasms of each species 

 than the observations presented by him in a later publication 

 justify. 



But if this much of restriction upon his conclusions may 

 be necessary, there still remains evidence of the most con- 

 vincing sort in his results of the specific nature of the pro- 

 toplasm of different species. The only details he has so 

 far given of his negative results are contained in his report 

 on sponge culture to the Bureau of Fisheries. In this he 

 describes experiments on intermingling the tissues of Micro- 



