34^ On the Echinoidea or Sea-Urchins. [Sess. 



elucidate its history is usually forthcoming. This " shell," 

 however, is simply the " test " or covering of a sea-urchin, 

 after all the " internal arrangements " of the animal have 

 been ruthlessly scooped out, and the exterior surface of the 

 shell has been stripped of its spines, and then, mayhap, 

 scraped, smoothed, and varnished. In this state it has very 

 little resemblance to the strange and uncanny looking animal 

 itself, when fresh from its native element, with its sharp 

 spines all set on end and in their lovely hues of pink and 

 crimson and rosy-purple. Eound the coasts of the Isle of 

 Man the common egg-urchin is very plentiful, and the fisher- 

 men eke out their scanty living by collecting them, cleaning 

 them out, and stripping off the spines, when the shells find 

 a ready sale amongst the crowds of tourists who annually 

 visit the island. 



Most modern scientific writers on the sea-urchins surround 

 the subject with a mass of technicalities, which renders an 

 otherwise interesting theme almost unintelligible except to 

 the initiated. Having had the opportunity lately of exani- 

 ining and studying a considerable number of these curious 

 marine animals, it has occurred to me that a paper dealing 

 with them in a popular yet accurate manner, and including 

 the results of the latest investigations on the subject, might 

 not be without interest to the members of the Society. 



In treating of the sea-urchins, and especially those of the 

 Firth of Forth, I shall first take as a type -specimen the 

 species which is most easily obtainable in our locality, and 

 which yet combines in itself all the important features of the 

 class — viz., the common egg-urchin {Eclmms sjihcera). This 

 species may be said to be plentiful in the Firth of Forth, 

 while a few others, to be afterwards mentioned, are more 

 sparingly found. Let us take a glance at the structure and 

 life-history of the common egg-urchin, and we shall then be 

 in a position to compare it with other Echinoids, as well 

 as with other members of the Echinodermata to which it 

 belongs. 



The group of the Echinodermata, or " thorny-skins," in- 

 cludes among its living forms the Asteroidea or Star-fishes, 

 the Ophiuroidea or Brittle-stars and Sand-stars, the Crinoidea 

 or Feather-stars, the Holothuroidea or Sea-cucumbers, as well 



