PLATK XI. 



Figs. 126 — 132, 137 — 140. — C. levinseni. 

 Fig- 133- — C. dodecalophus. 

 Figs. 134, 135. — C. gracilis. 

 Fig. 136. — C. sibogae. 



Figs. 126 — 128, 132, 130 are continuations of the series (C. levinseni) siievvn on PI. X. 



Fig. 126. — Twenty two sections further than fig. 125. — Through the oesophagus {oes.) The muscular 

 layer is thicker and narrower, indicating the approach of the stalk. The nerve-layer (ti.t.) is more 

 definite. [The oesophagus terminates in the si.xth section after fig. 126]. 



F"ig. 127. — Fourteen sections further. Through the beginning of the stalk [st.). 



Fig. 128. — Five sections further. The stalk [st.) is more distinct. 



Fig. 129. C. levinseni. — Frontal section of a young individual, shewing the position of the stalk {st.), 

 which is arranged as in Pi. I, fig. 5: — g.s.r., ventral (posterior) wall of right gill-slit; g.s.L, 

 left gill-slit; ph., folds of anterior (ventral) wall of pharynx; c.c., ventral wall of left collar-canal. 



Fig. 130. C. levinseni. — Seventeen sections further than fig. 132. Shewing the extension (b.c.^b.) of the 

 third body-cavity between the first {stovi.) and second [stoin.-) stomachs. 



Fig. 131. C. levinseni. — Obliquely transverse section of another individual: — f.c.r., right food-channel 

 between arm-base [a.b.) and right lobe of operculum [op.r.]. The ventral epithelium and basement- 

 membrane {b.ni.) of this part of the collar arc cut tangentially, so that the right collar-cavity 

 appears to be divided into two halves. The arrow indicates the course of the food to the mouth. 



Fig. 132. C. levinseni. — Four sections further than fig. 12S. The stalk, which is more liiL^hly magnified 

 than that of fig. 128, is now completely separate from the body. 



F'g- ^ZZ- C. dodecalophus. — Section of stalk, transverse to its principal axis. The epidermis is folded; 

 the nerve-layer has three principal concentrations, on the anterior side («. /.), but appears to 

 extend the whole way round the section. 



Fig. 134. C. gracilis. — Similar section of the stalk of the individual shewn in PL VI, figs. 60, 61, cut 

 near its junction with the body. 



Fig. 135. C. gracilis. — Section of another stalk. 



Fig. 136. C. sibogae. — Section of a stalk. 



Figs. 137, 138. C. levinseni. — Two frontal sections of a young individual. 



F'g- 1 37- — Through the dorsal part of the collar-cavities and the proboscis-pores (p.p.), which are seen 

 to traverse the central nervous system {c.n.s.). The epidermis of the collar is injured on the 

 left side. 



Fig. 138. — Two sections nearer the ventral side, through the pericardium [per.), the internal openings 

 of the proboscis-pores {p.p.), the notochord (nch.), and the anterior horns {b.c.^a.) of the collar- 

 cavities. 



F'ti- '39- ^- levinseni. — Sagittal section of anterior end of an individual with reversed proboscis: p.b., 

 pigment-band of proboscis; b.c.'-a., tip of anterior horn of the collar-cavity of the opposite side; 

 /., fold of wall of jjroboscis-stalk indicating the region where most of the twisting has probably 

 taken place. 



Fig. 140. C. lei'inseni. — Section through the left side of the individual shewn in PI. IV, figs. 34 — t,6: — 

 ph., tangential section of left edge of pharynx; g.s., gill-slit; c.c, collar-canal, in dilated condition. 

 The second arm {L.2) is cut along its groove. The fourth and fifth arms appear, in other sections, 

 in the positions indicated by L..f, L. j. 



[Figs. /.?_' — Ij6 were draivn tvith ZEISS, DD Obj., the others zcith C Obj. All are reduced ^/j]. 



