32 



NATURAL HISTORY 



completely from the parent, but to live right beside it, then each to bud 

 again, the result would be a compound organism, which might become 

 of considerable size. It is in just this way that the large masses of coral 

 do arise, a few of which are illustrated in our cuts. For instance, in 

 Astrcea the budding takes place in such a manner as to form a hemi- 

 spherical mass. The illustration shows a small specimen, in part of 

 which the polyps are expanded and in part retracted. 



In another group the polyps do not separate even so far as in Astrcea, 

 but remain more or less intimately connected with each other. Some of 

 these also form hemispherical masses sometimes two feet in diameter, 



Fig. 33. — Brain coral (HeliastrsBa) . The cut on the left shows the coral in the living condition; that on the 



right only the calcareous portion after removal of the rlesh. 



which from their shape and from the convolutions on their surface bear a 

 resemblance to the human brain, whence the common name, brain coral. 

 Our figures show the coral as it looks in the living condition, and also 

 after the animals have died and the fleshy portions have been removed. 

 The next cut shows three polyps from a brain coral enlarged. The three 

 mouths are visible, and the rows of tentacles are shown alonsr the sides ; 



but the reader will readily see that separation is not car- 

 ried so far as in Astrcea. 



Such corals as Astrcea and the brain corals are massive, 

 and play an important part by their solidity in the forma- 

 tion of coral reefs and islands, to be described shortly. 

 Their dead bodies form a foundation for other forms to 

 build on. All corals, however, have not this massive 

 polypi, 6 show! cnaracter 5 som e are delicate branching forms which 

 mgthe tentacles and alone would be ill adapted to the formation of a coral 

 reef, but, taken in connection with the others, they are 

 a considerable element, for their broken branches fill up the interstice 

 between the larger forms. 



Only one of these can be figured, the cleer's-horn coral (Madrepora), 

 one species of which is very common on the Florida coast. Here the 



Fig. 34. 

 coral 



