PLATE XI. 



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

 Fig. 133. — C. dodecalophus. 

 Figs. 134, 135. — C. gracilis. 

 Fig. 136. — C. sibogae. 



Fi^s. 126 — 128, 132, 130 are continuations of the series (C. levinseni) shewn 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 («. /.) is more 



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

 Fig. 127. — Fourteen sections further. Through the beginning of the stalk [st.). 

 Fig. 12S. — 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; ///., folds of anterior (ventral) wall of pharynx; cc, ventral wall of left collar-canal. 

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



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

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



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



membrane [b.m.) of this part of the collar are 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. 128. The stalk, which is more highly magnified 



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

 Fig- 133- C. dodecalophus. — Section of stalk, transverse to its principal axis. The epidermis is folded ; 



the nerve-iayer 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 PI. VI, figs. 60, 61, cut 



near its junction with the body. 

 F'g- 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. 

 Fig- 137- — Through the dorsal part of the coliar-cavities and the proboscis-pores (/./.), 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 coliar- 

 cavities. 

 Fig. 139. C. levinseni. — ■ Sagittal section of anterior end of an individual with reversed proboscis : /.(!'., 



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



ƒ., fold of wall of proboscis-stalk indicating the region where most of the twisting has probably 



taken place. 

 Fig. 140. C. levinseni. — Section through the left side of the individual shewn in PI. IV, figs. 34 — 16: — 



ph., tangential section of left edge of pharynx; g.s., gill-slit; cc, 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 /,. ^, Z.j. 



\Figs. 132 — 136 zvere drazun zvitli Zeiss, D D Obj., the other s zoith C Obj. All are reduced ^/j]. 



