652 
Fig. 
Vig. 
Fig. 
Fig. 
TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
tage 
40. 
4]. 
43. 
g. 44. 
Puate LV. 
Chaetopterus.—Trochophore. Optical section. x 40. 
(From a mounted specimen ome ., rectum, 
St., stomach. 
Chaetopterus.—Metatrochophore, ventral _—_ aspect. 
x 40. Fully contracted. #. ant., anterior pair 
of eyes, immediately in front of which a long rigid 
cilium is seen; &. post., right eyes of the two 
closely approximated posterior pairs. Mtr. 1 and 2. | 
anterior and posterior mesotrochs. 
Chaetopterus.—More advanced Metatrochophore than 
that of fig. 13; dorsal aspect. x .40. (Froma 
mounted specimen only.) Cd., caudal appendage ; 
S. sp., special setae of the fourth segment; U.-L., 
under-lip. 
Pectinaria.—Very early Metatrochophore, from the 
right side. 75. An. #., anal ridge. 
Pectinaria.—More advanced Metatrochophore with 
oesophagus protruded ; from the left side. x 75. 
(From a mounted specimen only.) An. R., anal 
ridge ; Oe., protruded oesophagus ; Pal., developing 
paleae seen through the body-wall. 
Pectinaria.—Metatrochophore almost ready for meta- 
morphosis; ventral aspect. x 75. (Krom a mounted 
specimen.) An. f#., anal ridge. The prototroch is 
indicated at the sides; its further course is 
marked by the absence of pigment except in the 
region of the mouth, where it could not be followed | 
precisely. 
Pectinaria.—Parts of the most advanced Metatrocho- 
phore seen. (A) Paleae as seen through the 
body-wall. x 120; (B) Posterior end, ventral 
aspect. x 75. To show the rudiment of the 
scapha (Sc.). 
Pectinavia.—Harly metamorphosis stage from the 
left side. X75. (From a mounted specimen 
only). Pal., paleae beginning to project from 
the body-wall; 7. lat., lateral tentacles. 
