SEA-FIR. 245 



Siphonoglyphe. Hickson, Ph. Tr. 174, 1883. 



Histology. Von Lendenfeld, Z. A. vi. 1883. 



Scissiparity. Andres, Mitth. Zool. Stat. Naples, ii. 1882. 



General Physiology. Solger, Biol. Centralbl. ii. 1882-83. Sense of smell. Pol- 

 lock and Romanes, J. L. S. xvi. 1883. Digestion. Metschnikoff, Z. A. iii. 1880; 

 Krukenberg, Vergleich. Physiol. Vortrage, ii. 1883, p. 53. Chromatology. Kruken- 

 berg, op. cit. iii. 1884, p. 125 ; MacMunn, P. R. S. xxxviii. 1884-85. 



Symbiosis. The term and general view, De Bary, Tageblatter der Versam- 

 lung der D. Natf. u. Aerzte, Cassel, 1878, p. 121 ; O. Hertwig, op. id. Freiburg, 

 i. B. Sept. 21, 1883, also sep. with a plate, 'Die Symbiose'; Fischer, Jena. 

 General account. Brandt, Arch. f. Anat. und Physiol. (Physiol. Abth.) 1882 ; 

 Id. Mitth. Zool. Stat. Naples, iv. 1883. Cf. Geddes, Nature, xxv. 1882; Brandt; 

 Moseley; Percival Wright; ibid. Geza Entz, Biol. Centralbl. ii. 1882-83. Klebs, 

 Biol. Centralbl. ii. Green bodies of Protozoa. Geza Entz. Biol. Centralbl. i. 1881-82. 

 Kessler, Arch. f. Anat. u. Physiol. (Physiol. Abth.) 1882. Miss Sallitt, Q. J. M. 

 xxiv. 1884. Of Hydra and Spongilla, Ray Lankester, Q. J. M. xxii. 1882. Of 

 Hydra, Hamann, Z. W. Z. xxxvii. 1882 ; cf. Ray Lankester, Nature, xxvii. 1882- 

 83, and Von Graff, Z. A. vii. 1884. Convoluta Schultzii, Geddes, P. R. S. xxviii. 

 1879; Barthelemy, C. R. 99, 1884; cf. on Vortex viridis. Von Graff, Z. A. 

 vii. 1884. 



Lichens. Sachs, Text-book of Botany, transl. by Vines, ed. 2, 1882, pp. 318- 

 330. Fungus of roots of trees. Nature, xxxiii. 1885-86, p. 212. 



50. SEA-FIR (Sertularia abietina), 



With Fig. ii, illustrating the structure of a Craspedote Medusa. 



THE Sea-fir belongs to the class Hydrozoa and order Hydroidea. It 

 forms a fixed colony or hydrosoma, which is protected in all its parts by a 

 yellowish chitinous perisarc. The hydrosome consists of a number of 

 hydranths or nutritive zooids collectively forming the tropJiosome and con- 

 nected to one another by a branching coenosarc. The hydranths are lodged 

 in perisarcal cups or hydrothecae ( = calycles), and are borne by a support- 

 ing plant-like structure or hydrophyton. This hydrophyton consists of the 

 coenosarc above-mentioned and its perisarcal investment. It is divisible 

 into a system of stems with branches, the hydrocaulus, and of rooting fibres, 

 the hydrorhiza, by which the colony is attached to some foreign object. 

 Numerous rooting fibres are to be seen at the base of this specimen. The 

 stems, with their branches, rise vertically from the root : they are somewhat 

 flattened and their two opposite edges are beset by the thecae for the 

 hydranths. The thecae on one edge of a branch or stem alternate more or 

 less accurately with the thecae on the other edge. The hydranths can be 

 completely retracted into their thecae and may be seen in this specimen 

 as opaque spots. The branching coenosarc is tubular. The walls of the 



