354 ^- 7- (joldfarb 



sea-water but in solutions diluted with about 20 per cent of tap- 

 water. The amount of salts present in this solution is most favor- 

 able to regeneration. As the quantity of salts is increased by 

 concentration or decreased by further dilution, the number regen- 

 erated decreases until the mimimum is reached on the one hand 

 at 45 per cent dilution and on the other at 58 per cent concentrated 

 sea-water. Stems transferred from concentrated to norm sea- 

 water which is equivalent to placing them in dilute solution, 

 regenerate according to the principle laid down, viz: the more 

 dilute the solution, to a certain point, the more hydranths pro- 

 duced. On the contrary, stems transferred from dilute to norm 

 sea-water, which is practically placing them into more concentrated 

 sea-water, do not regenerate less than stems continuously kept in 

 normal sea-water. Regeneration is not inhibited until the solu- 

 tion contains more salts than that normally present in sea-water, 

 while the stimulating effects of diluted sea-water occurs, when 

 either concentrated, normal or dilute solutions are diluted to 

 what is equivalent to a 20 per cent dilute sea-water. 



Before summarizing the internal factors, the behavior of the 

 ccenosarc under different conditions might perhaps more profit- 

 ably be taken up. 



The ccenosarc is circular in cross section, with no partition as 

 in the case of Tubularia. Granules within the ccenosarc stream 

 alternately toward the apical and basal ends, either in the same 

 direction throughout the colony or independently, in each branch, 

 or even in different directions in the main stem. The ccenosarc 

 itself can move en masse within the perisarc. fVith the basal Hvo- 

 thirds of stems excepted, the ccejiosarc invariably moves toward 

 the basal end of the piece, 1. e., in all branches, in the apical pieces 

 of stems, and m small pieces from any region of the colony. It may 

 even move entirely out of the piece, through the basal end. Noiv, as 

 regeneration occurs only where the ccenosarc is present, it follows 

 that whether regeneration, shall or shall not take place at a cut end 

 is determined by the migration of the ccenosarc. This movement 

 basally crowds or concentrates the ccenosarc at the basal end of the 

 piece and if conditions are favorable at the end polyps readily 

 appear there. The migration of the ccenosarc may be furthered 

 in various ways, namely: 



