REPORT ON THE ACTINIA IMA. 131 



Concluding Remarks. 



In the Introduction I have given a sketch of the structure of the Actiniaria, and 

 also at the same time a short summary of the most important morphological results 

 furnished by the Challenger material ; all that remains is for me to discuss how far the 

 results of the Challenger expedition have furthered our knowledge of the manner in which 

 the group in question is distributed. I have therefore made out a tabular survey 

 (p. 130) of the Actiniae described and their habitats, and have also stated whether or 

 not they are new species and genera. It follows, of course, that I have only enumerated 

 as new, such species as have been actually described for the first time by Moseley and 

 myself, whilst I have included among the known animals those forms to which, since we 

 know their anatomy more thoroughly, it has been necessary to give new names, especially 

 new generic names. 



The table in question gives no determinate results as to the geographical distribution 

 of the animals; it was, indeed, evident from the first that the Challenger material was 

 neither sufficient nor suitable for this purpose. The number of hauls made by the 

 dredge was utterly disproportioned to the vast tracts traversed by the ship in her voyage 

 round the world; the individual faunatic regions especially have been very irregularly 

 examined. As the ship was mostly on the high seas, the coasts, which would have 

 furnished the richest spoils, were of necessity almost entirely neglected, and in this way 

 we only find one littoral species in the list. 



On the other hand, we must take into special consideration the manner in which the 

 Actinise are distributed in the different depths of sea. How far is the number of the 

 Actinias diminished by the increase of the depth ? How far does the deep-sea fauna 

 vary from the fauna of the coasts and the shallows ? Has life in the depths exercised, 

 as in other cases, a visible influence on the organisation of the animal ? These are 

 questions which may be partially solved from the tolerably wide range of material furnished 

 by the Challenger collection. 



As a rule the number of the Actinias decreases as the depth increases; up to the present 

 they have not been observed even in the Challenger expedition at a depth of over 2900 

 fathoms, though the decrease does not take place so rapidly as might be expected. In 

 proof of this I contrast the results given by the hauls with the dredge in 10-500 fathoms, 

 with those in 500-2900 fathoms. The net was let down ninety-seven times in depths 

 of 10-500 fathoms, and eleven times with some result, i.e., with the capture of some 

 twenty specimens distributed over thirteen different species. There were one hundred and 

 sixty-five hauls with the dredge at depths of 500-2900 fathoms, fourteen of these fur- 

 nished about sixty specimens, representing twenty-one different sjjecies. These numbers 

 caimot of course be compared off hand, as the hauls made by the dredge in great depths 



