IJEPORT ON THE PKXNATTTLIDA. 



KEPOKT ON THE PENNATULIDA 



COLLECTED IN THE OBAN DREDGING EXCUKSION 



OF THE BIRMINGHAM NATURAL HISTORY AND 



MICROSCOPICAL SOCIETY, AUGUST, 1881. 



BY A. MILNES MARSHALL, M.A., D.SC, PROFESSOR OF ZOOLOGY 

 IN OWENS COLLEGE, AND W. P. MARSHALL, M.I.C.E. 



I C(i)tt tuned from p(i0e 9.) 

 4. — Anatomii of the PuJypes — 



The following description of the anatomical and microscopical 

 structure of the polypes is based on the examination of whole 

 specimens and of sections prepared in the manner already noticed. 



The structure of a polype is sliown in the series of figures on 

 Plate II. Fig. 10 shows a polype bisected longitudinall}- along its 

 whole lengtli ; Figs. 12, 13, 14 and 15 represent transverse sections 

 taken at various points of the length ; and Fig. 11 is a more highly 

 magnified section of one of the tentacles. 



The polype (Fig. 10) resembles in structure a somewhat elongated 

 Sea-anemone, consisting of a firm body-wall {k) continuous below 

 with the flesiiy coenenchym [1] of the rachis, and forming above a calyx 

 {g), which surrounds the tentacles (/') and has its free margin produced 

 into a series of eight pointed processes (Plate I., Fig 7), alternating with 



Descbiption of the Figures in Plate IL 



All the figures in this Plate are drawn from polypes taken from the largest 



living specimen. Fig 10 is constructed from a series of camera drawings taken 



from different specimens. Figs 11 to 15 are drawn with the camera from single 



sections. The magnifying power is indicated in diameters for each figure. 



Al phnhetical List of References. 



f. Tentacle. 



(J. Calyx. 



h. Cavity in calyx-process. 



i. Spicule. 



7c. Body-wall. 



p. Retractor muscle. 

 (/. Protractor iimscle. 

 r. Short mesenterial filament, 

 .s. Long mesenterial filament. 

 Ovum. 



I. Crenenchym, or fleshy body- I v. Smaller canals of ccpiienchym. 



substance. I w. Ectoderm. 



Ml. Mouth. X. Mesoderm. 



n. Stomach. y, Endoderm. 



0. Mesentery. I ,z. Thread-cell or nematoeyst. 



Fig. 10.— A single polyiie, with the part of tlie rachis from which it springs, 



bisected longitudinally along its whole length ; the plane of bisection adopted 



being the ^ilane of sijinmetry : shows the whole structure of one of the polypes, 



and the communication of its liody-cavity with the canal system of the rachis 



X 2-2. 



Fig. 11. — Transverse section through one of the tentacles at about the middle 

 of its length ; the section passing, on the right side, through the base of one of 

 the pinnules. Shows structure of tentacle aud pinnule and arrangement of 

 thread-cells, x 70. 



Fig. 1-2. — Transverse section through a polype at the line BB in Fig. 10 ; passing 

 through the calyx, the bases of tlie tentacles, and tlu; mouth, x 2ii. 



Fig. 13.— Transverse section through a polype at the line CC in Fig. 10, showing 

 the stomach and the mesenteries witli tlioir retractor muscles, x 2i2. 



Fig. 14. — Transverse S(!ction tlirough a polype at the line DD in Fig. 10, showing 

 the mesenteries with the retractor muscles, aud the long aud short mesenterial 

 filaments, x 22. 



F'ig. 1'). — Transverse section through the lower part of a polype at the line EE 

 in Fig. 10, showing the ova m situ, the long mesenterial filaments, and the open- 

 ings of the ccenenchymal canals into the body-cavity of the polype. 



