HEART-BODY, ETC., OF CERTAIN POLYCH^TA. 299 



31. Schneider (Guido).— (B.) ' Arb. Nat. Geo. Petersburg,' Bd. xxvii, 



Heft 1. (Ou the segmental organs and heart-body of Polychteta, witli 

 a German translation.) 



32. Steen.— Jena, 1883, ' Terebellides Stroemii' (Inaugural Disser- 



tation). 



33. WiREN. — ' Kongl. Svenska Vetenskaps-Akad. Handlingar,' Stoekholm, 



1885, 21, No. 7, pi. vi. 



EXPLANATION OF PLATES 19—22, 



Illustrating Mr. Lionel James Picton's paper " On the Heart- 

 body and Coelomic Fluid of certain Polychseta.^' 



PLATE 19. 



Pig. 1. — Audouinia fiiigera. Diagram of a dissection from the dorsal 

 surface. The head and posterior half of the worm are not represented. 

 The heart is represented as cut open, revealing the heart-body within it. 

 The arrows indicate the direction of the circulation. 



Fig. 2. — Audouinia fiiigera. Transverse section, x 115, through 

 widest part of heart-body. The cut strands of the heart-body are represented 

 lying in the heart, bathed by the blood (red), x. Blood between folds of the 

 heart-body. y. Lumen in heart-body. 



Pig. 3. — Anterior portion of young Polymnia nebulosa. Dorsal view ; 

 drawn whilst alive ; under low power. The heart-body is a dark rod inside 

 the dorsal vessel (heart). 



Pig. 4. — Pectinaria belgica. Transverse section of heart-body. 

 D objective (Zeiss). 



PLATE 20. 



All the figures in this plate refer to Audouinia fiiigera. 



Fig. 5. — Transverse section of a strand of the heart-body, showing endo- 

 thelium, cortex, and medulla. The last is occupied by yellow granules and 

 spherical spaces, which contain chitinous bodies, a. Granule in vacuole. 

 b. Large yellow granule. c. Granule deeply stained with hsematein. d. 

 Nuclei of medullary cells (the outlines of these cells are not evident), e. 

 Granular mass. 



