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 hystrioc 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 o{ 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. 74. 



