216 Dr. W. C. M'Intosh on the Zoophytes of St. Andrews. 



others, *by the late Dr. John Reicl, who obtained his examples 

 at St. Andrews. 



On the whole we lack at St. Andrews the splendid profusion 

 of the swimming jellies occasionally met with on our western 

 shores, and especially in the Outer Hebrides, to which a 

 favouring Avind and tide sweep them from the warmer area of 

 the Gulf-stream beyond, in company with lanthina and the 

 Pteropods. Amongst these the strange and beautifully tinted 

 Diphyes is seen darting hither and thither amongst the brilliant 

 blues of its brethren with its trailing fringes of bright orange 

 polypites ; and on the lonely western shores, as at Monach, 

 countless myriads of the little Velella are tossed in autumn on 

 the sand. 



Mr. Darwin *, referring to the colours of certain Invertebrate 

 animals, thinks that it is doubtful if such serve as a protection ; 

 but he goes on to observe that the perfect transparency of the 

 Medusae, " many floating mollusca, Crustacea, and even small 

 oceanic lislies partake of this same glass-like structure," and 

 that " we can hardly doubt that they thus escape the notice 

 of pelagic birds and other enemies." It seems to me somewhat 

 difficult to say what will escape the eye of a pelagic bird, such 

 as gull, guillemot, or hawk-like tern. Their keen eyes 

 distinguish very indistinct objects — for instance, the nucleus 

 of Salpa runcinata, and the minute and almost transparent 

 bodies of the young fishes that flit amongst the splendid masses 

 of swimming jellies (Molluscan and Coelenterate) which some- 

 times throng our western shores. The mere tremor of the 

 water is almost sufficient to attract such acute and skilful 

 marauders. Moreover, the statement of tlie great naturalist 

 is incomplete without the appendix that many of the Medusae 

 and Hydromedusre are brilliantly coloured and, in addition, 

 phosphorescent, the latter property likewise characterizing the 

 translucent Pyrosoma, and that my distinguished friend Prof. 

 Wyville Thomson regards the luminosity of marine animals 

 as a provision of nature for attracting their enemies in the 

 abysses of the ocean, or for throwing a flood of light on their 

 own prey. I have already t shown my reasons for believing 

 that the theory of the latter author is open to doubt, and shall 

 make a few further remarks on the subject under the Annelida. 

 If the notion had been promulgated that the sexes in the 

 abysses of the ocean used their light to attract each other, and 

 thus had a better chance of continuing the race, perhaps more 

 might have been said in its favour. 



* Descent of Man, &c. 



t Ann. & Mag. Nat. Hist. ser. 4, vol. ix. 1872, p. 2. 



