MARINE BIOLOGICAL STATION AT PORT ERIN. 91 



All the leading sections of existing Echinodermata 

 are found at Port Erin, as follows : — 



Crinoids, Feather-stars : Antedon bifida (fig. VII., 

 1) is found in deep water off the cliffs, and often occurs 

 in considerable numbers on the wicker creels used in the 

 capture of crabs and lobsters, to which it clings 

 tenaciously by means of its claw-like cirri. Its colour is 

 variable. Some specimens are deep red, but the majority 

 are of a dirty yellow tint, more or less mottled with rose 

 colour, hence the name " Rosy Eeather-star " often given 

 to this animal. While it often remains in one position 

 for a considerable time, Antedon can swim by means of its 

 ten feathery arms, which are alternately flexed and 

 extended with much grace and vigour. The food of 

 Antedon consists of Diatoms and Infusoria (see fig. I.), 

 which are caught by the delicate tentacles of the arms 

 and passed along minute grooves in the latter to the 

 mouth. 



In the young (" pentacrinoid ") stage Antedon is 

 fixed by a long stalk to the blades of the great brown oar- 

 weed (Laminaria) as shown at 2, and magnified at 3. The 

 pipe-like " Encrinites," so abundant in the limestone of 

 Derbyshire and elsewhere, are the fossilised remains of 

 the stalks of Crinoids, which flourished in the seas of the 

 Carboniferous period, and some of which were of very 

 large size. 



Asterids : Asterias rubens, the common star-fish 

 (fig. VIII. , 2), is the most familiar example of this group. 

 The mouth is in the centre of the under surface of the 

 disc, from which' the five rays or arms radiate. A deep 

 groove, in which the numerous tube-feet are lodged, 

 traverses the under surface of each arm, and at the 

 extremity of each groove, just below the tip of each arm, 

 there is an orange-red spot, the eye. In addition to the 



