28 
to transparency similar to that of horn was observable. These cir- 
cumstances have also been observed in the madreporites of Gothland. 
But those which are generally met with in this island are of a dark 
ash colour, the ridges, however, of these, formed by the transverse plates 
of the corals, give them very much of the appearance which has just been 
noticed. 
Attributing the formation of these corals to the operations of the 
madreporean or medusean polype, let us endeavour to trace the little 
architect through its wonderful labours. Agreeable to the observa- 
tions of Donati, each of the legs, as he terms them, of the polype 
are provided with two processes which are applied to each side of one 
of the perpendicular laminae, whilst a muscular pyriform body, attached 
to the other end of the leg, gives to it the power of employing that 
motion which is necessary for the accomplishment of its task. The 
young polype, disposed on an appropriate spot, may be considered as 
completing its operations by two distinct processes : the secretion and 
separation of carbonate of lime from the sea-water, conveyed through 
the pyriform body ; and its deposition, at its moment of secretion, 
by the two small processes, where the economy of the animal directs. 
Proportioned to the number of legs possessed by the infant animal, was 
probably the number of perpendicular laminae, or pillars converging to 
the centre, which it began to erect; these when raised to a certain 
height, appearing to have been connected together by a horizontal plate 
of the same substance. On these the animal erected similar pillars, 
and placed on these a covering similar to that with which he had 
completed the first compartment. Thus seems to have proceeded the 
incessant labours of the minute artist : and as the number of its legs, 
or instruments, increased, and as they extended in length, so must the 
number of the perpendicular laminae, and the circumference of the 
horizontal plates have also augmented. Thus must this curious fabric 
have derived its fashion from the growth and form of this minute and 
wonderful animal. 
