56 



MEDUSAE OF THE WORLD. 



The chief and possibly only well-marked point of difference between the forms S. mira- 

 bilis and S. tubulosa is that in the hydroid of S, mirabilis the medusa-buds arise from near 

 the base of the polypite, whereas in the hydroid of 5. tubulosa they arise from points higher 

 up on the sides of the polypite, between the tentacles. 



20. 



FIG. 19. Sarsia eximia, after Hartlaub, in Nordischcs Plankton. 



FIG. 20. Syncoryne eximia, after Allman, in Ray Society, 1871-72. Hydroid'and young medusa. 



