REGENERATION IN THE ANNELID WORM AMPHINOMA PACIFICA, 

 AFTER REMOVAL OF THE CENTRAL NERVOUS SYSTEM. 



By a. J. GOLDFARB. 



In a previous publication/ the writer found that the head of the earth- 

 worm Lumbricus was regenerated in the entire and permanent absence of 

 the nerve-cord from the amputated region. Inasmuch as this was the first 

 demonstrative experiment of a complete and perfect regeneration in the 

 absence of the nerve-cord, it seemed extremely important to ascertain 

 whether the phenomenon was peculiar to Lumbricus, and therefore of 

 limited significance, or whether other annelid worms could likewise regen- 

 erate without the aid or presence of the nerve-cord. With this object in 

 view, the marine annelid Amphinoma pacifica was chosen, because it lives 

 so well in the laboratory, because large numbers could be readily procured, 

 but especially, because it was sufficiently large and hardy to permit of the 

 necessary operations. 



There were two types of operations : 



1. After narcotizing in a 5 per cent solution of alcohol in sea-water, the 

 worms were amputated and the nerve-cord extracted. This was done by 

 passing a fine forceps into the coelomic cavity in such a manner that the 

 nerve-cord lay between the tongs of the forceps, and at any desired position 

 the forceps were firmly brought together and the contained nerve-cord 

 was extracted with its ganglia and bases of the nerves. These could then be 

 readily counted. I never succeeded in getting pieces so long as those 

 in the earthworm, illustrated in my report.^ I did succeed in extracting as 

 many as nine consecutive ganglia. This method had the distinct advantage 

 of causing very little injury to adjoining tissues. The importance of this 

 fact will be later emphasized. 



2. The second type of operation, used by Morgan^ and modified by 

 Nussbaum,' consisted in cutting a "window" from the ventral side near 

 the amputated level. The parts so removed or injured included cuticle, . 

 muscle layers, nerve-cord, often the ventral blood-vessel, and the nephridia. 

 A modification of the operation consisted in making a ventral incision, then 



' Goldfarb, A. J. The influence of the nervous system in regeneration. Jour. Exp. Zool., 7. 4. PP- 643- 

 722. 1909. 



2 Morgan, T. H. Experimental studies of the internal factors of regeneration in the earthworm. Arch 

 fur Entw. Mech., 14. 1902. . 



' Nussbaum, J. Beitrage zur Frage uber die Abhangigkeit der Regeneration vom nervensystem bei 

 Nereis diversicolor. Arch. f. Entw., vol. 25. 1908. 



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