W. C. M'Intosli on the Abyssal Theory of Light. 7 



the body was still faintly luminous, while from the injured 

 points the soft parts protruded. A pale Aphlehino. {Poly- 

 cirrus) , very generally distributed, is so phosphorescent that, on 

 simply blowing on the Avater of the dissecting-trough or other 

 shallow vessel in which it lies, the most vivid pale bluish lumi- 

 nosity gleams for a moment along every one of the mobile ten- 

 tacles, which are often elegantly disposed in a stellate manner. 

 Now, with the exception of Harmothoe imhricata and Eunoa, 

 all the luminous annelids above-mentioned are inhabitants 

 of tubes of greater or less density. Chcetopterus lives under 

 stones between tide-marks, amongst old shells and stones in 

 deep water, or sunk in sand and gravel at low water in tubes 

 resembling thick parchment covered with pebbles, shells, and 

 seaweeds. Polynoe scolopendrina frequents the tubes of the 

 speckled Terebella nebulosa ; indeed I have never found it any- 

 where else than in these or similar galleries. The latter species 

 is not luminous, while the former is ; yet both are placed 

 under the same circumstances, and, of the two, perhaps P. sco- 

 lopendrina has less need for such extraneous aid in procuring 

 nourishment. Many of the Polynoidte which have similar 

 habits are not phosphorescent, while the succeeding form, 

 which greatly resembles Terebella in habits and structure, is 

 luminous. With such a varied history, the only theory that 

 seems feasible is one which would endow the Polynoe with the 

 property of attracting prey for the benefit of Terebella or itself 

 — a somewhat analogous part to that ascribed by the fancy of 

 the older naturalists to the pea-crab in the horse-mussel ! The 

 yellow Aphlebina^ again, a close ally of T'erebella^ is beautifully 

 phosphorescent. This and the two foregoing are compara- 

 tively safe from the attacks of marauding fishes or crabs, the 

 two former in tubes immersed in sand or under stones, and the 

 latter in obscure chinks and fissures of muddy rocks, boulders, 

 and old shells. It will not do to affirm that they are pro- 

 tected because they are luminous, since many species which 

 are not so have exactly the same habits and shelter, while 

 other phosphorescent annelids are without such a safeguard. 

 Lastly, Eusyllis occurs in swarms in delicate tubes on Lami- 

 narian blades covered with Obelia^ as well as under ascidians 

 on stones between tide-marks. The effect produced in its 

 former situation may sometimes be seen on a gigantic scale on 

 the West Sands at St. Andrews, after a heavy storm has 

 tossed on shore a bank of tangles and other seaweeds about a 

 mile long. Throughout this extent, Avherever the people are 

 engaged at night in securing the valuable mass as manure, 

 countless myriads of minute glittering points cover the sea- 

 weeds, carts, and weapons. Whether the phosphorescence be 



