Fig. 14. A portion (0°2 mm. from the tip) of a seta 
(2.5 mm. long) from a littoral specimen 125 mm. long. 
On the left the lamina, with its dentate margin, is shown. 
x 800. 
Fig. 15. Two crotchets from neuropodia of a post- 
larval specimen 5'1 mm. long. The teeth on the sides of 
the rostrum are indicated. The dotted line indicates the 
level of the epidermis. x 1,000. 
Fig. 16. Neuropodial crotchet from a young littoral 
specunen 17 mm. long. x 500. 
Fig. 17. Neuropodial crotchet from a littoral speci- 
men 125mm. long. x 150. 
Fig. 18. Ventral portion of neuropodium of Lami- 
narian specimen 250 mm. long. On the left (which is 
ventral) the various stages of formation of the crotchets 
are seen. The crotchet on the right is fully formed. 
Vin shows outline of the neuropodial sac. eit). 
On comparing the four preceding figures there is seen 
to be, as the worm grows, an increase in the length of the 
crotchets, a decrease in the size of the teeth behind the 
rostrum, and also a gradual change in the inclination of 
the rostrum to the shaft, the angle increasing with the 
size of the specimen. 
Fig. 19. Right aspect of ninth and tenth chetigerous 
segments of Laminarian specunen (190 mm. long). The 
fourth gill has eleven main stems united at their bases by 
a membrane. Five of these, and many lateral branches, 
have been cut away to show the remainder. The ventral 
stem alone, in which the lateral branches have the 
simplest form, is shown entire. Lateral branches some- 
what simplified. Fig. 21 shows one in detail. The 
third gill has been almost entirely cut away. The 
capillary sete are seen projecting beyond the lips of the 
notopodial setal sac. Kach neuropodium resembles a 
