ALCYONIUM. HI 



fashion, and the pinnules are somewhat con- 

 tracted. The stomodaeum (St.) and the six 

 short and two long mesenterial filaments 

 may be seen through the transparent 

 body- wail. At the base of the crown of 

 tentacles, and at the region where the antho- 

 codia abuts on the general surface of the 

 colony the body-wall is rather more opaque 

 owing to the presence of several spicules. 

 Fig. 5. A diagram of a section through a portion of a 

 lobe, to show the mode of communication 

 between the polyp cavities in the inner parts 

 of the colon}'. 



Plate II. 



Fig. (J. Transverse section through an expanded antho- 

 codia in the region of the stomodaeum, show- 

 ing the siphonoglyph (Si.), the folded 

 epithelium on the rest of the stomodaeum 

 (St.) the arrangement of the retractor muscles 

 (Msc.) on the mesenteries, and the structure 

 of the body-wall. Ed. = Ectoderm. Mes. = 

 Mesogloea, and End. = Endoderm. 



Fig. 7. A series of stages of the final development of 

 the spermatozoa as seen in a preparation 

 made by breaking open a spermary in 

 December, a. a ripe spermatozoon, b. c. d. 

 and e stages in the formation of the tail, f. a 

 cell with four nuclei occasionally met with in 

 these preparations. 



Fig. 8. A cnidoblast, containing an immature 

 nematocyst. 



Fig. 9. A mature nematocyst. 



Figs. 10 and 11. Two nematocysts after their discharge. 



