330 A. J. GoUjarb 



stems regenerate in 3 days, 50 per cent at the oral and 45 per cent 

 at basal ends. Inverted stems — with basal ends pointing toward 

 the zenith — in the same time, regenerates 35 per cent at the oral 

 and 60 per cent at the basal ends. The figures for 6 days empha- 

 size the point, viz: Erect stems regenerate 50 per cent at the oral, 

 80 per cent at basal ends, inverted stems 35 per cent at oral and 

 115 per cent at basal ends. 



Injury to different parts of a stem does not affect the regenera- 

 tion at the axial ends of the stem. Nor does increasingly diluted or 

 concentrated sea-water influence the number of hydranths at 

 basal or oral ends. Heteromorphosis occurs independently of 

 these influences. 





\ 



\ 

 \ 

 \ 



\ 



COENOSARC^ 



, The coenosarc may readily be observed in the 



~ ~ more distal parts of a colony, for the perisarc there 



is thin, almost transparent and seldom covered with 

 debris, polyzoans or hydroids, commonly found 

 on the more basal regions. The coenosarc is com- 

 - - -f posed of a hollow cylinder surrounded by the 

 perisarc. The lumen, within the coenosarc is cir- 

 cular in cross section and differs from Tubularia^" 

 n in which the lumen is divided into two almost sepa- 

 / rate compartments by a central partition along 



•1 the whole length of the stem. 

 / It has already been pointed out that the number 



of hydranths regenerated at the oral or at the basal 

 / ends, depends upon whether lateral branches or 



~~ stems were used, and if the latter, upon the re- 

 7" ~ ~~J gion from which the piece was taken. Previous 

 experiments and direct observations prove conclu- 

 sively that the coenosarc withdraws from the distal 



Fig. 2 



"Gast and Godlewski's account of the coenosarc in Pennaria cavolinii is extremely interesting in 

 this connection. Hargitt, G. T., '03 gives an account of the histologic structure of the coenosarc. Archiv 

 fiir Ent., Bd. 17. 



^■^StevenSjN. M., '02 records movements of the coenosarc in Archiv f. Ent., Bd. 15. Stevens '01, '02, 

 .'Vrchiv f. Ent., Bd. 13 and 15. 



