MARINE BIOLOGICAL STATION AT PORT ERIN. 33 



loscomhii, Gapulus himgaricics, Scaphander lignariuSy 

 Otina otis, Bulla hydatis, and Melampus hidentatus, 

 mostly from Bay Fine. 



Molgula citrina and Ascidia depressa are mider stones 

 near Port St. Mary, and many species of compomid 

 Ascidians, especially Botryllids, such as Botryllus morio, 

 B. aurolineatics , B. violaceus, and Botrylloides albicans, 

 are common both at Port Erin and Port St. Mary. 



Protective Colouring. 



The common shore prawn, Virhius varians,iomidi2^i Port 

 Erin, and probably all round the coast, is a most marked 

 case of protective colouring. Specimens taken from a 

 "zostera prairie" are of the same bright green colour as 

 the "Sea grass," to the blades of which they adhere 

 closely, (see PL VI. fig. 3). Their eggs also are green. 

 Specimens, however, which are found amongst the red 

 sea- weeds, such as half rotten masses of Delesseria and 

 Bhodymenia (see fig. 2), are either completely red, or red 

 with a slight mottling of white or grey. Specnnens found 

 on a sandy bottom, or on small gravel, are mottled black, 

 grey and white. These are all cases of simple, but very 

 complete, protective colouration. 



The specimens of Virbiiis, however, which occur upon 

 the dark brown sea- weed Halidrys siliquosa present a more 

 comphcated case, as they actually mimic the chambered 

 capsules of the Alga, both in form and colour, and also 

 in position. The Crustacean is here of a dark brown 

 colour, and has the habit of clinging to the stem in such 

 a position that the body extends straight outwards m a 

 stiff attitude (see PI. VI. fig. 1) ; and the plant may be 

 shaken to some extent without affecting the pose of the 

 Crustacean, and its resemblance to the capsules. 



These are clear cases of the Crustaceans having become 



