240 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



tional points of interest. In certain instances ova were joined together and 

 agglutinated with each other, as in the experiments of de Haan and zur Stras- 

 sen; in others, early embryonal stages were combined (Driesch, Goldfarb). 



Driesch united two blastulae of Echinidae and observed that they were able 

 to form one organism with twice the number of cells, but the individual cells 

 did not coalesce. A single organism developed presumably if contact mecha- 

 nisms or contact substances acting as regulators were favorable to such a 

 union ; otherwise, separate organisms resulted. Apparently the stage at which 

 the joining together of the component parts took place and the size of the 

 surfaces which agglutinated (Goldfarb), and probably also the degree of 

 specificity of tissue and organ differentials, determined the outcome of the 

 operation. The further the differentiation had progressed, the more pro- 

 nounced was the tendency on the part of the partners to separate again and 

 to give origin to two distinct organisms. If one organism had been produced, 

 the inner organs appeared to be double or they had united into single organs. 

 In some cases two larvae formed, which had certain organs, such as gut, 

 skeleton or body cavity, in common, while in other cases these organs re- 

 mained separate. When one partner dominated, as so often occurs in mam- 

 malian parabiosis, distintegration of the skeleton could take place in the 

 weaker partner, and as a result of such degenerative processes a single larva 

 developed, in which the gut of the dominant larva supplied the remnants of 

 the other partner with food ; furthermore, it was observed that even mesen- 

 chyme cells could move from one larva into the other. Agglutination was, in 

 these experiments, preliminary to coalescence and we may assume that it took 

 place readily if the consistency of the cells was suitable for this process. 

 According to Herbst and Driesch, lack of Ca and a certain degree of alka- 

 linity or low temperature in the surrounding medium caused stickiness and 

 favored agglutination of the cell surfaces. In Driesch's experiments it is not 

 indicated whether he had to deal with syngenesious or homoiogenous relations 

 between the partners ; but in Goldfarb's experiments, both syngenesious and 

 homoiogenous unions succeeded. In the investigations of Morgan in Echini- 

 dae, parts of brothers were successfully joined together in syngenesious 

 transplantations. He observed that processes of degeneration or atrophy in 

 one of the partners could precede the transformation of the combination into 

 a single larva, but there were also found all transitions between a single 

 homoiogenous organism and double organisms. Goldfarb, as well as Bierens 

 de Haan, showed in Echinidae that as many as forty eggs could be made to 

 agglutinate with one another, but that a combination of more than two eggs 

 rarely developed beyond an early embryonal stage. Thus an incompatibility 

 became noticeable, comparable to that observed in transplantation of primitive 

 adult invertebrate organisms, where likewise the difficulty in the integration 

 of the parts into one whole seemed to increase the more the greater the number 

 of pieces which were joined together. 



Of general interest are also the experiments of zur Strassen, who showed 

 that in Ascaris two unfertilized eggs could coalesce, and that there was present 



