POLYCH ZT LARVAS. 653 
Wig. 45. Pectinaria.—Later metamorphosis stage; from the left 
side. >< 75. (From a mounted specimen.) 
L., compressed lobes of the ventral surface ; Pal., 
paleae ; Ptr., probable position of the prototroch 
(visible during life only, and therefore indicated 
by a dotted line); Sc., scapha; T. lat., lateral 
tentacle; 7. med., median tentacle. 
Wig. 46. Pectinaria. Tubicolous stage before the commence- 
ment of life on the sea-bottom; ventral aspect. 
x 75. (From a preserved specimen only.) L., 
compressed lobes of the ventral surface; Pal., 
paleae; Sc., scapha; T. lat. 1 and 2, right lateral 
tentacles (of outer and inner pair respectively) ; 
T. med., median tentacle; Tb., tube secreted by 
the worm; Ttr ?, remnant of telotroch ? 
Vig. 47. Pectinaria.—Parts of the, Metatrochophore as seen 
during life, to show the arrangement of the cilia. 
(A) Anal segment from behind; (B) Posterior end 
from the right side; (C) Oral region from the right 
side; An., anus; An. #., anal ridge; C. an., delicate 
cilia round the anus; C. trans., transverse row of 
cilia at the anterior end of the neurotroch; C. or., 
oral cilia;  Nir., neurotroch; Ptr., prototroch ; 
Sph., spherical prominence immediately behind 
the posterior end of the neurotroch; T. C. Nir., 
tuft of cilia in which the neurotroch terminates ; 
T. C. or., tuft of cilia which marks the posterior 
boundary of the oral ciliated region; Tir., 
telotroch. 
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