EXPERIMENTALLY FUSED LARV/E OF ECHINODERMS WITH SPECIAL 

 REFERENCE TO THEIR SKELETONS. 



By a. J. GOLDFARB. 



The early work of Loeb, Morgan, and Herbst on the production of 

 multiple embryos from a single egg suggested the reverse experiment of 

 grafting or reuniting several fertilized eggs into one embryo. This im- 

 portant experiment was first performed by Driesch, who succeeded in 

 grafting together two eggs in about 0.04 per cent of the culture. With the 

 same technique he subsequently grafted the eggs in other species of echino- 

 derms and succeeded in keeping such grafted groups alive until they had 

 developed into the larval or pluteus stage. He found that these larvae, fell 

 into several distinct types, as follows: true twins, twins with a common 

 blastocoele, twins with a reciprocal influence on growth, fusion with a 

 partially double archenteron, perfect fusion with a single set of organs, and 

 single body with a second parasitic archenteron. 



In 1912, the writer repeated these experiments with the American form 

 Arbacia punctulata and succeeded only after slightly modifying Driesch's 

 method. In the best cultures about 40 per cent were fused in groups of 2, 

 3, 4 or more eggs. These fused groups were preserved at different stages of 

 development for further detailed study, but sufficient precautions had not 

 been taken to guard against the solution of the very delicate skeletal struc- 

 tures of the larvce. Consequently the early stages only were available for 

 detailed and complete study. Such studies corroborated and extended the 

 results of Driesch. 



Subsequently, in the performance of other experiments, it was discovered 

 that eggs could be agglutinated and fused quite as readily by a very different 

 method, which was not only simpler but free of certain objections that might 

 be urged against previously known methods. The new method consisted 

 in using an isotonic or slightly hypotonic NaCl solution diluted with varying 

 quantities of sea-water. 



NEW METHOD OF FUSING EMBRYOS. 



The best results were obtained by the following procedure : The eggs of 

 Toxopneustes were artificially fertilized, and 15 to 20 minutes later approxi- 

 mately equal quantities were placed in solutions made up of 70 to 80 parts 

 of 5/8 m. NaCl (isotonic with sea-water at the Tortugas) and 30 to 20 parts 

 of sea-water. After 5 to 8 hours in these solutions the eggs were trans- 



10.=; 



