BERMUDA BIOLOGICAL STATION. 569 



is a greater wealth and variety of life than can he found in an equal 

 area elsewhere in all the Bermuda archipelago. Located on the very- 

 edge of the outer reef, where breakers are always running, save in 

 perfectly calm weather, the conditions seem to be especially favorable 

 for many of the marine organisms. Numerous small and brilliantly 

 colored fishes dart about in the pools, and escape into the crevices of 

 the rock as one attempts to scoop them up. The great black sea- 

 urchin (Diadema setosum) bristling with slender spines is firmly en- 

 sconced in niches in the rocky floor and usually defies all attempts at 

 removal. But by breaking away the rim of protecting rock this urchin 

 may sometimes be dislodged. Unless great care is used, however, his 

 spines, which are like needles, will penetrate the flesh, where they 

 are sure to break off and become a source of great irritation if not 

 promptly removed; but they are so brittle that removal is not an easy 

 matter. Crabs both great and small are everywhere, and the little 

 hermits with their molluscan shelters of various kinds and sizes make 

 a grotesque appearance as they scuttle away to cover. 



One of the most novel sights that I saw in these tropical seas was 

 viewed through a water-glass near North Bocks. A school of small 

 fishes (Atherina) swimming in a nearly spherical mass ten or fifteen 

 feet in diameter, seemed to be slowly revolving through the water as 

 its individuals swam round and round in an almost solid mass. It 

 was not at first apparent how the mass preserved such a constant form, 

 but at length it was seen that a few individuals of another and larger 

 species of fish were acting the part of the shepherd dog, and that 

 the smaller fishes were actually being herded — a flock of submarine 

 sheep. Xor do the herding fishes prey upon their flocks. The ex- 

 planation is interesting. Three kinds of fishes are involved in this 

 association. The herders accompany and ' round up ' the smaller 

 fishes, so that other kinds of fish which are wont to prey upon them 

 may, as they approach with murderous intent, fall victims to the 

 herders. 



Bicturesque Castle Island, which still contains ruins of early forti- 

 fications, — some of them possibly dating from the early part of the 

 seventeenth century, — once guarded the entrance from the sea through 

 the channel of Castle Boads. From the floor of this channel the 

 dredge brings up many interesting animals : the great conchs 

 (Strombus gigas), the shells of which are still prized by tourists, 

 living Foraminifera of several kinds, and, best of all. the Caribbean 

 A m pliioxus. This species was dredged in considerable numbers at 

 various places during the summer of 1903, and especial attention 

 was given during the past summer to finding out how widely it is 

 distributed, and the conditions under which it thrives. As a result 



VOL. LXVI. — 37. 



