THE SYMMETRY OF GRAFTED EGGS IN RELATION 

 TO GIANT LARV.E FORMATION IN ARBACIA 



PUNCTULATA. 



A. J. GOLDFARB, 



COLLEGE OF THE CITY OF NEW YORK, AND MARINE BIOLOGICAL LABORATORY, 



WOODS HOLE, MASS. 



TABLE OF CONTENTS. 



PAGE 



Introduction 21 



Single Larvae, Axes of Two Grafted Members Unknown 22 



Single Larvae, Axes of Two Grafted Members Known 23 



Single Larvae, Absorption of One Member 24 



Change of Axes During Development 27 



Summary and Conclusions 31 



Bibliography 32 



INTRODUCTION. 



Two or more eggs have been experimentally grafted together 

 by several investigators (Driesch, Goldfarb and de Hahn, 2, 3, 

 4. 5, 6, 7 and 8), who have also described some of the types of 

 larvae resulting from such grafts. One of these types, the Riesen- 

 larva, first produced and described by Driesch, has aroused 

 considerable interest particularly with respect to its origin. This 

 larva is distinguished from other fused larvae, in that it is normal 

 in structure, single, and identical with control larvae, except for 

 size. According to Boveri (i) and de Hahn (5) such perfect 

 fusion into a single larva can occur only when the axes of the 

 fusing eggs are so placed that they bear the same relation to 

 each other as the blastomeres of the two cell stage of an egg; 

 i. e., the axes and the planes of the two grafted eggs must be 

 parallel and symmetrical. 



In studying separate clusters of grafted eggs of the sea-urchin 

 Arbacia punctulata, 1 and in following the development of each 

 cluster through its pluteus larva, numerous facts were disclosed 

 that did not accord with Boveri's hypothesis of the genesis of the 

 Riesenlarva. A concise statement of these facts is given below, 



1 For technique of grafting, see Goldfarb 6 and 7. 



21 



