Objects for the Microscope. 209 



CALCAREOUS SPICULES OF DORIS. 



The Doris is a soft-bodied animal, often called a sea- 

 slug ; it is one of the Nudibranch mollusca, having its 

 breathing organs outside its body, and like a starry plume 

 on its back. It is often seen gliding about in sunny rock- 

 pools, or sheltered under loose stones feeding on sponges, 

 and also on dead fish. The tongue is very beautiful, and 

 has been noticed amongst the palates. 



CALCAREOUS SKELETON OF DORIS. 



The skin appears to be strengthened by these calcareous 

 spicules as a kind of skeleton, and their position is better 

 viewed when thus mounted. 



The shape of the spicules varies a little with the species. 



SPICULES OF GORGONIA. 



These slides present a variety of calcareous spicules, 

 which, when examined with the J-inch power and dark- 

 ground illumination, or simply with polarized light, show 

 curious shapes and beautiful colours. They are found in 

 the skin of the Gorgonia, and each species has its peculiar 

 shape and colour. 



Gorgonias are zoophytes ; when drawn up from the 

 ocean, as they live at a great depth, they look like a shrub 

 or small tree of bright salmon colour ; the branches are 

 spotted with little depressions, but have no appearance of 

 life. If, however, it is quickly replaced in sea-water, a 

 lovely sight is seen from every dot, on every branch, 

 comes forth a living creature, flower-like, pearly white, and 

 spreading forth a circle of delicate pinnae or filaments, edging- 

 eight petal-like tentacula. They are feeling for their prey, 

 and drawing in shoals of marine infusoria, like other 

 zoophytes. When the animals die, the petals shrink in and 

 the skin hardens, and these spicules are found in masses 

 throughout. Some the Gorgonia cristata have spicules 

 shaped like double crosses ; some are of a rich purple ; 

 others crimson ; others again of golden hue even by natural 

 transmitted light and with moderate power. 



