MARINE BIOLOGICAL STATION AT PORT ERIN. 105 



No. 3 is Clavelina, where beautifully transparent indi- 

 viduals are united by a creeping root. It is sometimes 

 found in the deeper pools at Port Erin. 



The egg of an Ascidian develops into a minute 

 tadpole-shaped larva which has a back-bone running along 

 its tail and a nervous system with a brain, containing an 

 eye and an ear. In fact, the structure of this Ascidian larva 

 is very like that of any young vertebrate animal, and if it 

 remained in this condition for life it would be proper to 

 classify it along with the lowest fish-like vertebrates. But 

 it does not so remain. After a brief free-swimming 

 existence it becomes attached to a rock or sea-weed, and 

 settles down for the rest of its life. Then degeneration 

 sets in. The backbone, the brain, the eye and the ear — 

 all the evidence of its high organisation and active early 

 life — break up and disappear, and the free tadpole becomes 

 reduced to the sedentary sack-like Ascidian. This life- 

 history is a good example of degeneration, but it also 

 shows us that Ascidians are derived from ancestors which 

 were once related to the backboned animals. 



There is one of the Tunicata which remains free- 

 swimming all its life, and has a backbone in its tail. It 

 is called Appendicularia, and we frequently catch it in the 

 tow-net in Port Erin bay. 



The reports upon the Tunicata in our series are by 

 Professor Herdman, and the first of the L.M.B.C. Memoirs 

 is on " Ascidia." 



FISHES. 



(Fig. XXII.) 



There are about 150 different kinds of fishes found in 

 the Irish Sea around the Isle of Man. Some of these are 

 the well-known edible fish belonging chiefly to the Cod 



