24 A. J. GOLDFARB. 



Another double gastrula is shown in Fig. 15, in which the two 

 guts are unequal and in which the axes are bent at an angle 

 approximately 45 degrees. This double gastrula developed 24 hours 

 later into a "single" larva, and normal except for a slight swelling 

 of the body wall in the aboral region on one side. Fifty-four 

 hours later it developed into a very large larva (Fig. 16), whose 

 body, skeleton and digestive tract are "single" and normal 

 except for the hypertrophied bar in the aboral region marked X. 



I have records of ten other similar pairs of grafted gastrulae 

 in which the relative sizes of the guts and the axial angle varied, 

 yet in spite of this asymmetry, all of them developed into 

 "single" larvse like those just described. Two other pairs are 

 described in the next section (see Figs. 26 and 34). 



In these instances at least, the particular angle formed by the 

 axes is not correlated with the formation of Riesenlarva, and in 

 all of them in spite of marked axial asymmetry, the two members 

 fused into perfect or nearly perfect "single" larva, and Riesenlarvce. 



SINGLE LARV.E BY ABSORPTION OF ONE MEMBER. 



In all the clusters under consideration there ivas no separation 

 of the two members. Separation frequently occurred especially in 

 agglutinated pairs, but such specimens were of no significance in 

 these studies and are oniitted from consideration. All of the 

 "single" larvae described in this paper had their genesis in a pair 

 of more or less completely and permanently fused blastulae or 

 gastrulae. 



Many grafting experiments have shown that a resorption of 

 parts often takes place, and it was conceivable that in these 

 experiments resorption or disintegration of one of the members 

 might also have taken place. Before any conclusion can be 

 drawn it must be definitely shown whether resorption or dis- 

 integration occurred and the nature and degree of resorption. 

 The following examples will throw some light on this phase of 

 the problem. 



Fig. 17 is clearly a fused pair of blastulae approximately equal 

 in size. During the next twenty-four hours the two developed 

 very unequally, one into a gastrula and then into a young pluteus, 

 while the other ceased developing and then decreased in size 



