26 A. J. GOLDFARB. 



organism as in these fused larvse. These and other facts (see 

 Goldfarb 7 and 8) appear to me to indicate that one of the 

 members is not disintegrated, nor merely absorbed. It appears 

 to me that the cells of the smaller or weaker or more slowly 

 differentiating member are translocated, into the dominant mem- 

 ber, where the translocated cells are regrouped into additional 

 gut, skeleton or body wall, and in cases of incomplete regulation, 

 into accessory parts. 



Absorption and translocation of cells of one member may take 

 place even after both members have fully differentiated their 

 guts, and the axes of both members was definitely fixed. For 

 example, two grafted eggs developed into a double fused gastrula, 

 one somewhat larger than the other and with axes about 90 

 degrees apart. A free-hand sketch is shown in Fig. 26. During 

 the next twenty-four hours the smaller gastrula was gradually 

 absorbed, while the other continued its normal development. 

 The resulting larva which is shown in Fig. 27 consists of one body, 

 one skeleton, all normal except for the small accessory bars at 

 the aboral swollen end of the body. During the next two days 

 the larva became decidedly larger, the swelling at the aboral end 

 smaller and concomitant with these changes, two accessory parts 

 of the gut appeared (Fig. 28). During the next three days 

 while the body gradually diminished towards the normal, THE 



ACCESSORY GUTS LIKEWISE DISAPPEARED AS WELL AS THE ACCES- 

 SORY SKELETAL PARTS, transforming the larva into a completely 

 normal one (Fig. 29), indistinguishable from control larvae. 



In this instance the two fused gastrulae, although their axes 

 were 90 degrees apart, gave rise to a "single" larva, as did the 

 paired gastrula of the preceding section. // the intermediate 

 steps in the development had not been observed, one might have 

 concluded either that this larva was derived from a single egg, or 

 from a symmetrical pair of eggs as required by the Bvveri-de Hahn 

 hypothesis. But it is evident that the process was quite different, 

 that there was first a gradual and definite absorption of one member, 

 a translocation or migration of parts, an increase in the volume 

 and mimber of parts of the dominant member, and finally a loss of 

 materials and parts. 



These successive changes do not always give rise to normal 



