SEA-MATS AND SHELLY COEALLINES. 63 



form of the same class of animals. Meanwhile, I will 

 just point out a beautiful though minute proof of design 

 in a point of the structure of the cells connected with these 

 pearly chambers. If you look closely, you will see that 

 the spines of the margin are not found on those cells that 

 carry the pearls ; and moreover, that they are also wanting 

 on the approximate edges of the two cells that lie behind 

 every such pearl-bearing cell. Now the reason of this 

 omission is obvious. The spines projecting obliquely 

 would interfere with the gaping of the door ; and hence 

 they are invariably absent there. 



I happen to have in my aquarium a living individual of 

 another species belonging to the same class, and agreeing 

 with this in all essential particulars of structure, though 

 widely different in form. The difference, however, is 

 mainly dependent on a rather unimportant point of ar- 

 rangement ; for the cells, instead of being set side by side 

 and end to end, in quincunx fashion, to an indefinite 

 extent, on two surfaces of a plane, are disposed on one 

 single surface, and in longitudinal rows of two or three 

 cells abreast ; thus narrow ribbon-like branches are 

 formed, which now and then divide into two, then these 

 into two more, and so on. These branches thus become 

 fan-shaped, which, by being slightly curved, became seg- 

 ments of funnels ; and the peculiar elegance of this coral- 

 line consists in the mode in which these branches are set 

 on the stem, viz., in an ascending spiral curve, so that the 

 effect is that of several imperfect funnels set one within 

 another, but which yet you perceive, by turning the whole 

 gradually round, to compose a single corkscrew band of 

 successive fans. This whole structure stands upright in 

 its natural state, like a little compact shrub growing from 

 a root; and as a good many are commonly associated 

 together, they form a sort of mimic grove, fringing the 

 sides of dark rocky sea-pools. 



The species is called the Corkscrew Coralline, or, some- 



