ANTHOZOA OF THE WOODS HOLE REGION. 23 1 



to be rather common in Metridium marginatum, as I have found many cases occurring, 

 both in the aquarium and in a state of nature. Torrey (op. cit.), has suggested that it 

 may be due to the unfavorable conditions of the aquarium, but its occurrence in natural 

 conditions as just cited would preclude this as a cause. 



DISTRIBUTION. 



Anthozoa are of wide distribution, both in time (geological) and in space (geograph- 

 ical), and also in bathymetrical range. Of the first, or geological, it is not within the 

 scope of the present paper to take notice. Of geographical range it may sufBce to say 

 that, like the former, a general consideration of the problem is not designed in the present 

 review. Many conditions are involved in the matter of distribution, among which 

 temperature plays an important part. This is particularly the case with alcyonaria, 

 which are predominantly tropical or subtropical organisms. The same may also be said 

 of the coral group, or Zoanthariae. 



In bathymetrical range there is great variation among the several groups. Many 

 of each have been dredged from great depths, but by far the larger number have their 

 habitat in shallower seas and along shore lines. In certain cases a given species may 

 find itself equally at home in depths of from 50 to 1,500 fathoms. Bathyactis is recorded 

 as being found in depths of from 50 to 3,000 fathoms. 



ECONOMIC RELATIONS. 



In common with coelenterates in general, the economic relations of Anthozoa are 

 chiefly incidental and indirect. A few fishes are known to feed on corals, a few on 

 hydroids, perhaps still fewer on alcyonarians or others. So far as I am aware, actinians 

 are usually immune from predatory attacks. Furthermore, certain actinians may 

 serve as hiding places for small fishes, which have established commensal relations with 

 them. On the other hand, not a few actinians feed upon fishes more or less freely. 

 The commensal relations of actinians and hermit crabs are well known. 



Indirectly corals have played a very important part in the contour of islands and 

 continents from Paleozoic to recent times. And at present in subtropical regions these 

 organisms are constantly concerned in the extension of certain coast lines by the forma- 

 tions of reefs along its margins. Thus, may be reclaimed something of the areas 

 constantly being lost through erosion and transportation of continental debris into the 

 seas; but, on the other hand, growth of these organisms in harbors and roadways of 

 steamships often involve obstructions and (dangers hard to overcome. 



SYSTEMATIC ACCOUNT. 



In common with that of other classes of coelenterates, existing conditions of 

 taxonomy of Anthozoa are not highly satisfactory. Several attempts at revision have 

 been made within comparatively recent times, but much yet remains to be done before 

 an orderly and adequate system of classification will be established. Among those who 



