STRUCTURE, ETC., OP CERATA OF NUDIBEANOHS. 59 



5. The large^ elaborately branched parieto-cerata of D e n d r o- 

 notus are merely a further development of the small tufted 

 parieto-cerata of Tritonia, and although they may on account 

 of their extended surfaces have secondarily acquired to a certain 

 extent a respiratory function^ they cannot be regarded as 

 specialised branchise. 



6. The cerata, whether they are large branched parieto- 

 cerata as in DendronotuSj or hepato-cerata containing the 

 greater part of the liver as in Do to, or having cnidophorous 

 sacs in addition as in Eolisj are not of primary importance 

 either in respiration or in digestion, but give to the animals, 

 by their varied shapes and colours, appearances which are in 

 some cases protective and mimetic, and in others conspicuous 

 and warning, as may be found best suited to their individual 

 surroundings and mode of life. 



EXPLANATION OF PLATES VI, VII, VIII, IX, X, 



Illustrating Prof. W. A. Herdman's paper " On the Structure 

 and Functions of the Cerata or Dorsal Papillae in some 

 Nudibranchiate Mollusca." 



a. Artery, ap. Aperture of cnidophorous sac. b. c. Blood-corpuscles. 

 br., br'^., br^. Brauchise. b. s. Blood-space, c, c\, c". Cerata. ctt. s. Cnido- 

 phorous sac. c. t. Connecting tube between hepatic csecum and cnidophorous 

 sac. c. tis. Connective tissue, d. I. v. Dorso-lateral vein. ec. Ectoderm. 

 ec'. Invaginated ectoderm-cells (cnidocysts) which produce cuida. ec" . Young 

 cnidocysts or cells of cnidophorous sac, f. Eoot. /. gl. Foot-glands, g. Gang- 

 lion, gl. Gland-cells, h. c. Hepatic caecum, h. c. Narrow part of hepatic 

 caecum in the body of Doto. j. Junction of Cerata with body in Do to. 

 k. Folds of the integument. /. Liver, I. m. Longitudinal muscles, m. 

 Muscle-bands. »*'. Longitudinal muscle-bands in body of Dendronotus. 

 m. I. Median part of liver in body of Doto. mes. Mesodermal tissues, n. 



