224 THE MICROSCOPE. 



MADREPORID.E. 



Madrepores, Mother-pores, or " tree corals," differ from other corals 

 in not having a smooth skeleton, but one inducted by numbers of small 

 cells for the residence of the living animal : these are very visible in 

 the Madrepore muricata, when the polyp is dead and decomposed ; but 

 most distinct in the Oculina ramea, or Abrotanoide, as they are situated 

 at the apparently broken stumps that branch from the trunk of the 

 skeleton (Plate V. fig. 5). Every branch is seen to be covered 

 with multitudes of small pits or dots, scarcely visible to unassisted 

 vision ; but when viewed under the microscope, will be found to 

 be cells of the most beautiful construction, remarkable alike for their 

 mathematical regularity and the exquisite fineness of the materials em- 

 ployed in their composition. A magnified drawing of one of the cells 

 is given at No. 6. The living polyps are most beautiful in their native 

 waters ; their varying colours adding to the richness of the hues cover- 

 ing the plains of the ocean. 



Caryophillia, or Nut-leaf. The Caryopliittia Smithii is found 

 tightly fixed to rocks ; it is round, of a dirty white colour. Dr. Fle- 

 ming says of the plates : " The lamellae are disposed in fours, and may 

 be distinguished into three different kinds. The first are the highest 

 and the broadest at the margin ; but as they descend into the disk, they 

 become narrower before they join the central plate. The second kind 

 are narrower than the preceding at the margin, but towards the middle 

 they suddenly enlarge and join the middle plate. The third kind are 

 the smallest, and terminate before reaching the middle plate. The 

 space included between a pair of the first kind of plates contains one 

 of the second kind in the middle, with one of the third kind in each of 

 the lateral spaces. Those on the sides are rough, with small scattered 

 tubercles, and their margins are curled. This last circumstance occa- 

 sions the roughness externally, where the longitudinal striae are the 

 remains of the gills. The plate which occupies the bottom of the 

 cavity is smooth, variously twisted, and connected with the base of the 

 lateral plates." 



Dr. Coldstream, writing to his friend Dr. Johnston, gives the fol- 

 lowing interesting account of the animal : " When the soft parts are 

 fully expanded, the appearance of the whole animal resembles very 

 closely that of an Actinia. When shrunk, they are almost entirely hid 

 amongst the radiating plates. The specimens I have seen have varied 

 in size from three-tenths to half an inch in height. They are found 

 pendent from large boulders of sandstone, just at low-water mark; 



