236 



NATURAL HISTORY OP OUR SHORES 



From half tide to the lowest littoral zone, wherever slabs 

 of rock overhang, or where some large boulder is sup- 

 ported, cromlechlike, upon others, vast colonies of the 



Fig. 100. Botryllus morio, on fucus 

 Natural size 



common " Sea-squirt " may be seen, densely crowded, on 

 the under side. 



These are Cynthia aggregata. They are of a deep red 

 colour, with the projecting tips of the apertures of a lighter 

 red. They range from the size of a pea to that of a small 

 walnut. Smaller allied forms (the nomenclature of which 



