370 Dr. Johnston on the British Annelides, 



pearly hue, and the skin is thickly covered with minute vesi- 

 cular granules (fig 13.), similar to those which are seen on 

 certain parts of the foot. The use of these is probably to give 

 the worm a firmer hold on the ground, and prevent any retro- 

 grade movement from the various evolutions of the feet. In 

 examining this complicated structure it is scarcely possible to 

 refrain from some expression of surprise. " In figuris ani- 

 mantium (etiam minutarum) quam solers subtilisque de- 

 scriptio partium, quamque admirabilis fabrica membrorum ! 

 Omnia, enim, quae quidem intus inclusa sunt, ita nata atque 

 ita locata sunt, ut nihil eorum supervacaneum sit, nihil ad 

 vitam detinendam non necessarium*.^^ 



From the remarks of Audouin and Milne-Edwards, it ap- 

 pears that Aphrodita hystrix is subject to considerable va- 

 riety in size, shape, and in the length of its feetf ; and of 

 course it would be frivolous to found any distinction of spe- 

 cies on these particulars. But an inspection of their figure 

 shows Aph. hystrix to be a more hispid worm than the one 

 now described ; and there are other characters which seem to 

 me sufficient to prove them distinct. I propose therefore to 

 call the British species Aph. borealis; and the specific cha- 

 racters of the two species may be thus given : — 

 Aph. hystrix, scales naked; proboscis with minute jaws; 

 some bristles of the dorsal foot serrulate at their points ; 

 those of the ventral foot somewhat forked ; inferior cirrus 

 very short, — Aud. and Milne-Edwards, Litt. de la France, 

 ii. p. 70. pi. 1. fig. 1—9. 

 Aph. borealis, scales naked; proboscis edentulous ; all the 

 bristles of the feet smooth ; those of the ventral foot sim- 

 ple ; inferior cirrus rather long, 

 Plate X. Fig. 1. Aph, borealis of the natural size. 2. The same on the 

 ventral aspect. 3. The anterior part magnified. 4. The same seen from 

 below. 5. The proboscis laid open. 6. An outline of a foot. 7. The 

 ventral branch of a foot more highly magnified. 8. Two spines. 9. Bristles 

 of the superior fascicle. 10. A filiform bristle. 11. A bristle from the 

 ventral branch. 12. Bristles from the inferior fascicle of the dorsal branch. 

 13. A portion of the skin of the belly magnified. 



The Nereides in this collection were, 1. Nereis margarita- 



* Cicero de Nat. Deor. lib. 2. 



t Hist. Nat. du Litt. de la France, ii. p. 71. 



