TWO SPECIES OF HYDRACTINIA 
493 
20 
,'7 
HYDKACTIXIA SPIRALIS^ 
Fig. 20 Transverse section of a colony at right angles to the mouth of the shell. 
The details of the cellular parts are not shown, a outer chitinous lamella, h inner 
chitinous lamella, c endodermal tube, d blastostyle, c superficial hydrorhiza, 90 
diam. 
Fig. 21 Nutritive polyp. 45 diam. Fig. 22 Nutritive polyp. 45 diam. 
Fig. 23 Blastostyle. 45 diam. 
