STRUCTURE, ETC., OF CERATA OP NQDIBRANOHS. 61 



Fig. 11. — Transverse sectiou of An cul a through the lateral paired branchiai 

 {dr-.) S. 1. 



Fig. 12. — Vertical section of part of base of lateral branch ia. S. i. 



Fig. 13. — Tritouia (Candiella) pie bei a, from right side. X 3. 



Fig. 14. — Outline of transverse section of Tritonia plebeia through 

 rhinophores, showing processes of the body-wall {k.). S. 1. 



Fig. 15. — Outline of transverse section of Tritonia plebeia through 

 middle of body, showing cerata. S. 1. 



PLATE VIII. 



Fig. 16. — Dendronotus arborescens from the left side. Natural size. 



Fig. 17. — Transverse section of Dendronotus near the middle of the 

 body, showing one of the second pair of cerata cut in longitudinal section 

 (c-.). The relative positions of the liver (/.), short hepatic caecum {/i. c), 

 ceratal blood-sinus {c. s.), and dorso-lateral veins {d. I. v.) are shown. S. 1 

 (reduced). 



Fig. 18. — Transverse section of one of the third cerata of Dendronotus, 

 showing the solid mesoderm {rnes.) containing muscles (/«.) and ceratal blood- 

 sinuses (c. s.). S. i. 



Fig. 19. — Transverse section near the base of one of the cerata cut off 

 the living animal, rapidly hardened, cut in the freezing microtome, and ex- 

 amined unstained in water, to show the distribution of the dark-brown 

 pigment. S. 1. 



Fig. 20. — A small piece of the mesodermal tissue as seen in some sections 

 of the cerata, to show the lacunae containing blood-corpuscles. S. \. 



Fig. 21. — A section near the top of one of the cerata, from a specimen 

 killed with corrosive sublimate and glacial acetic acid, then hardened gradually 

 with alcohols of different strengths, soaked in gum, cut with the freezing 

 microtome, and stained with picro-carmine, to show the masses of gland-cells 

 lying in meshes of connective tissue. S. \. 



PLATE IX. 



Fig. 22. — Outline of Doto coronata, from the left side, x 3. 



Fig. 23. — Transverse section of Doto coronata through the posterior 

 part of the body, showing the large cerata and their contained hepatic ca;ca 

 (Ji. c). S. 1. 



Fig. 24. — Part of a similar transverse section more highly magnified, showiu"- 

 the junction of one of the cerata with the body. S. \. 



Fig. 25. — Part of another similar section, showing the continuation of the 

 hepatic csecum {h. cK) into the body alongside the ovo4estis (o. L). S. ^. 



