3O A. J. GOLDFARB. 



If on the other hand there is but a single example of the 

 development of a Riesenlarva from asymmetrical members, it 

 suffices to overthrow Boveri's theory. And it is unnecessary to 

 demonstrate that two grafted members must be symmetrical. 

 But in four examples at least the axes and planes were clearly 

 asymmetrical, yet they developed into Riesenlarva. At least 

 five others were cited in which the axis of only one member was 

 known, but which also developed into single larvae. And it is 

 highly improbable that in all these instances the axis of the 

 second member should by a rare combination of circumstances 

 have been blastomerically symmetrical -with the known member. 



From these results it must be evident that not all Riesenlarva 

 are formed by the fusion of blastomerically symmetrical eggs. 

 While Riesenlarva .may be formed in this manner, my observa- 

 tions lead me to conclude that the more common method is by a 

 resultant of many and complicated processes which may briefly 

 be summarized as follows: (i) One member develops normally 

 and completely, the other is arrested in its development, rarely 

 proceeding beyond the gastrula stage. (2) The arrested member 

 is subsequently absorbed, very gradually, and some or all of the 

 cells translocated. (3) The translocated mesenchyme cells form 

 additional skeletal material either making a giant skeleton pos- 

 sible or forming accessory skeletal bars or rods. A translocation 

 of endoderm cells also, either helps in the making of a giant gut, 

 or in forming accessory parts to the gut. (4) With reduction in 

 size, consequent upon starvation of the plutei in the later stages, 

 some or all of these accessory parts tend to disappear. The 

 result of all these changes is frequently a single typical Riesen- 

 larva or atypic double larvae. In other words the factors making 

 for complete regulation are either not associated with original 

 symmetry of the grafted pair, or with any subsequent symmetry, 

 or they play a very minor role. 



Of far greater importance is: (i) the stage in development 

 when fusion takes place; (2) and inequality in the fusing pairs. 

 The earlier the fusion the more complete is it, and the greater 

 the tendency to perfect fusion and Riesenlarva formation. This 

 was in part observed by both Driesch and de Hahn, and Goldfarb. 

 At least any difference in the two fusing members either in size 



