12 PHYSIOLOGICAL SERIES. 



material and wedge-shaped bars of calcareous matter in 

 nearly equal proportion. The calcareous bars show on 

 section a finely laminate structure with radial striation. 

 PI. VIII. fig. 1. 



A. 38. Eunicella verrucosa, and diagram of its structure. The 

 axis is composed of horny matter disposed in layers. At 

 the growing tips of the branches the central first-formed 

 portion is spongy and contains much water. This form of 

 axis being elastic and strong is probably best fitted to resist 

 injury, and is the type most prevalent amongst Gorgonacea. 

 PI. VIII. fig. 2. Presented by Prof. C. Stewart. 



G. v. Koch, Morph. Jahrb., Bd. iv. 1878, p. 269. 



ALCYONARIA that live with the lower end of the stem 

 imbedded in mud or fine sand. 



Kolliker, Anat. Syst. Beschr. d. Alcyonarien, i. Pen- 

 natuliden, 1872. 



A. 39. A Sea-pen (Pennatula phosphorea), laid open to expose 

 the slender cylindrical axis, which consists of an intimate 

 mixture of calcium carbonate and organic matter. 0. C. 88. 



Hunterian. 



A. 40. A Sea-pen (Pennatula grisea), laid open along the 

 anterior aspect to expose the central axis. Large needle- 

 shaped spicules are abundant in the pinnules. 0. C. 227. 



Hunterian. 



A. 41. A longitudinal section of Pennatula grisea, exhibiting the 

 structure of the central stem. 0. C. 228. Hunttrian. 



ECHINODERMATA. 



42. A Feather-star (Antedon rosaced). The endoskeleton is 

 composed of a great number of small pieces formed in the 

 connective tissue. They consist of a minute network of 

 combined calcium carbonate and organic matter. The 

 network usually first appears in the substance of inter- 

 communicating cell-processes. The connective tissue of 



