antheadjE. 149 



to be peculiar, and which suggests the notion that the 

 effect is produced more by the distension of the column 

 than by the contraction of the disk. In these cases, too, 

 the slightest touch (which, in a Sagartia or Actinia, under 

 similar circumstances, would only cause a closer contrac- 

 tion) is followed by the instant recession of the column, 

 and the protrusion of the tentacles. 



The whole body manifests comparatively little contrac- 

 tility. The shrinking of the parts from every touch, which 

 in the Bunodidce and the Sagartiadcs is so excessive, going 

 on even after decomposition has set in, and which is so 

 annoying and so baffling to the anatomist, prevails to a 

 far less degree in the Antheadce; and hence the family 

 presents favourable conditions for dissection. The power 

 of discharging mucus is also comparatively small. 



Though ordinarily adherent by the base, the power of 

 adhesion is unwontedly feeble in the family ; the animals 

 can be detached with the slightest force, and often spon- 

 taneously free themselves. Both of our British genera 

 have the habit of frequently crawling to the brim of the 

 water, and then expanding their base upon the surface 

 and allowing it to dry, floating by means of it with the 

 body inverted, and the tentacles expanded in mid-water. 



An attentive observer sees in the habits of the Antheadce, 

 and particularly in the lively and flexuous movements of 

 the tentacles, an indication of superior muscular power in 

 these organs, and also a higher degree of intelligence, or 

 at least of perceptive faculty, than the Sagartiadce possess. 



Besides our own two genera, Aiptasia and Anthea, 

 one or two exotic genera must belong to the family. 

 If Mr. Dana has correctly described the Act. flagellifera of 

 Madeira, it must be generically distinct, notwithstanding its 

 very close resemblance in figure and colour to the green 

 variety of Anihea cereus. He speaks of the inner row of 



