DEVELOPMENT OF THE PECTINIBRANCHIATA. 353 



Fig. 10. Embryo from the side, a-g, as in the foregoing figures; h, eyes; 

 i, tentacles ; k, proboscis. 



Fig. 11. Young Buccinum seen laterally, a, shell; b, mantle; </, lobes; 

 e, heart; /, foot ; g, auditory organ ; h, operculum ; z, head ; k, eyes; 

 /, tentacles; m, mouth; w, stomach; o, intestine; p, branchiae; 

 q^ bladder ; r, liver ; s, muscles ; t, cerebral ganglia ; u, commissures ; 

 V, pedal ganglia ; x, commissure ; y, ganglia of the pedal lobes. 



Fig. 12. Young seen laterally. The same letters as in the foregoing figures, 

 except 0, salivary glands ; p, cerebral ganglia ; g', commissure ; 

 r, pedal ganglia, with their nerves ; s, ganglia of the pedal lobe ; 

 <, commissure ; u, siphon ; v, branchiae. 



Fig. 13. Dorsal view of young, a, shell; 6, mantle; c, foot; d, head; 

 e, eyes ; /, tentacles ; g, siphon. 



Fig. 14. Nervous system of a young individual seen laterally and compressed. 

 a, head; 6, eyes; c, tentacles; c?, foot; e, oesophagus ;/, cerebral 

 ganglia ; g, optic nerve ; h, auditory nerve ; i, commissure ; ^, pedal 

 ganglia; /, nerves of the foot ; m, commissure; w, ganglion of the 

 pedal lobes ; o, its nervous branches ; p, intestinal nerve. 



Fig. 15. One of the lobes, X 400. a, primitive longitudinal tubes; b, trans- 

 verse simple tubes ; c, calcareous granules ; d, cilia ; e, cirrhi. 



Fig.. 16. Eyes of an embryo, X 400. a, capsules whose external and internal 

 surfaces are ciliated ; b, membrane enclosing pigment granules. 



Purpura lapillus, Plate XI. . 



Fig. 1. Ovigerous capsule, containing ova in different states and of the natural 



size. 

 Fig. 2. An egg magnified. «, chorion ; 6, vitelline membrane; c, yelk. 

 Figs. 3, 4, 5, 6, 7, 8. Ova, in various stages of cleavage, magnified. 

 Fig. 9. Embryo magnified, a, ciliated membrane ; b, cells. 

 Fig. 10. Embryo many days older, a, ciliated membrane ; b, peripheral cells ; 



c, central cells. 

 Fig. 10 6. The same, X 350. 



Fig. 11. An embryo at nearly the same stage of development. 



Fig. 12. A rather more advanced embryo, viewed laterally, o, membrane; 



b, the two lobes ; c, the rudimentary foot. 

 Fig. 13. An embryo, viewed laterally, X 350. o, shell; b, lobes; c, foot. 

 Fig. 14. An embryo, viewed laterally, X 350. a, shell; b, lobe; c, foot; 



d, mantle. 



Fig. 15. An embryo, viewed dorsally, X 380. a, shell; 6, lobes ; c, foot ; 

 df mantle. 



Fig. 16. An embryo, x 350. a, shell, in which calcareous granules are depo- 

 sited; 6, lobes; c, foot; d, auditory organ ; e, rudiments of the sali- 

 vary gland J /, mantle. 



Figs. 17, 18, 19, 20, 21, 22, 23. Ova in different stages of development. 



Fig. 24. Grouped ova. 



Fig. 25. Ovum, slightly magnified, and taken out of the capsule to show the 

 result of the grouping, a, grouped ova, which have not yet taken a 

 decided form ; h, embryo in the earliest state. 

 SCIEN. MliM.~iVa^ Hist, Vol. I. Part IV. 23 



