172 POPULAR HISTOTIY OF THE AQUARIUM. 



stem. It was called Pentacrinus Europcuus. Here was a 

 living Encrinite. The column was flexible, and bent at the 

 will of the animal ; its base w^s attached to marine animals 

 by a broad calcareous disc. In the year 1836, Mr. Thomp- 

 son communicated the result of further researches in a me- 

 moir published in the Edinburgh 'New Philosophical Jour- 

 nal/ from which it appeared that his Pentacrinus Europcpus 

 was nothing but a Feather-star in a young state ; and that 

 the Comatidai in fact, began life as a fixed star and ended 

 it as a wandering comet. In other words, the starry head 

 floats off the stem, and the animal becomes free. 



" First, like a polype, bending on its stem, 

 Its rays are spread, a stany diadem ; 

 It feels new powers, it struggles to be free, 

 Then roams at large, unfettered in the sea." 



In some tribes the reverse of this takes place, and the ani- 

 mal, free in infancy, becomes grave and sedentary with age. 

 The gradations marking the change in Comattda are traced 

 and explained by Mr. Tliompson. He observed the advanced 

 Pentacrinite beginning to form piunse ; then the dorsal cirrhi 

 increased from fivs to nine ; then the detached Comatula, in 

 which the pinn?e are nearly complete. These small ComatulcB 

 retain the original yellow colour of the Pentacrinite near 



