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FAMILY III.— ANTHEAD^. 
In my “ Synopsis of the British Actinige,” (see Annals 
of Nat. Hist, for June 1858,) I had associated Antliea with 
Actinia, in one family, distinguished by the negative 
character of lacking suckers, warts, and loop-holes. But 
groups founded on negative characters are always unsatis- 
factory ; and maturer consideration has convinced me that 
the positive diversities of these genera are of sufficient im- 
portance to warrant their separation into distinct families. 
The members of the family Antheadce are marked by 
a great development of the tentacular system. The tenta- 
cles extend to a remarkable length, — in the typical genus 
often reaching to twice or thrice the diameter of the disk, — 
and are very flexuous. These organs have thinner walls 
than usual, but are lined with a thick coat of comparatively 
large pigment-grains of a deep brown hue. They show 
a greater tendency to discharge the water which ordinarily 
distends them, by contracting in diameter than in length, 
the effect of which is, that these organs under irritation 
collapse into a shrivelled or withered condition. 
Another remarkable peculiarity is the almost total in- 
ability to retract the disk and tentacles, and to close over 
them the margin of the column, — tlie common mode in 
which Actinioids seek protection from annoyance. It is 
true that, on rare occasions, and when perfectly undisturbed, 
I have seen both Anthea and Aiptasia in this retracted 
condition ; but still, even then, there is a tenseness and 
globularity in the covering column which is at once seen 
