4(') KKCKNT MAnUKlMKAKIA "I' TIIK HAWAIIAN ISLANDS AND LAYSAN. 



The pnccdiny t:ii)lc shows tluit all tlu" strictly rccf-huildiiiK v^cneva live at a 

 teinpenitui'f of Tii-'-TS'^ F. 



The li>t uiulcr 73 —60^ F. contains tho namos of 9 g-cnora whiili were not found at 

 a temperature so liiuh as 70' F. Seven of these 9 were also found at a temperature 

 between 40^ and 50'. The 5 genera I'ouiul hetween CO and 50^ were also found 

 1>et\veen 50 and 40". 



The genera occurring between 70- and 40" are precisely the same as those occur- 

 ring between the loo and 400 fathoms lines. They are Turbinolids, Eupsaimnids, 

 .some slendei- liianching Oculinids and Stylophorids, and also some fragile Fungids. 

 The greatest number of genera was found between 40° and 50° F. in temperature 

 and between KIO and 200 fathon;s in dt'pth. Eleven of the 17 genera found between 

 40 and 50^ F. occur ])etween the 100 and 200 fathoms lines, while 11 of the 13 

 genera collected between 100 and 200 fathoms live at a temperature between 40° 

 and 50"". 



TcMiiperature and depth, then, can he coupled. The best conditions for a profu.se 

 development of Turhinolitl genera are, (l)a depth of 1O0-200 fathoms, and (2) a tem- 

 perature of 4() -50 F. 



It should be emphasized that these concbi.sioiis apply to the Hawaiian Islands, 

 and that more extensive studies are necessary V)efore th(> fundamental principles of 

 control of distrii)ution by de[)th and tcinjicraturc can lie tirndy established. 



INFLUENCE OF THE CHARACTER OF THE BOTTOM ON DISTRIBUTION. 



.Vt first 1 thought that the <liaracter of tlie bottom might intluencc the species of 

 corals growing on it. l)ut a glance down the general table, containing the names of 

 the species, the station numbers, depth, etc.. shows that the same species occurs on 

 so great a \aricly of bottom that its importance as a factor in determining di.stribu- 

 tion is doubtful. cxce()t the water probaliiy nuist be clear and the corals must have 

 objects to which they can attach themselves. 



ADDITIONAL FACTORS GOVERNING THE DISTRIBUTION OF MADREPORARIA. 



Dana says: "The range of temperature 85- to 74 gives sufficient heat for the 

 development of the greater part of coral-reef species; and yet the temperature at the 

 loo-foot plane in the middle Pacific is mostly above 74"^. The chief cause of limitation 

 in depth is the diminished light, as pointed out by Prof. T. Fuchs."" 



Pressure and diminished light are both correlative with depth. Both factors 

 need further investigation. Another factor that needs study is the food supply; 

 and probably the oxygen content of the water. Some of the factors to which 

 considerable attention has been paid are not considered here, such as position with 

 reference to the lines of the breakers, relations to the fall and rise of the tides, etc. 



As yet comparatively few facts bearing upon the fundamental principles which 

 determine the distribution of corals have been collected. Most authors have con- 

 tented themselves with merely mentioiung the station and depth at which a given 

 form was procured; they usually have not utilized even these data in attempts to 

 discover any underlying principles. We need much more information and more 



"Corals and Coral I.slandi', 3d ed., p. 118. 



