CHAPTER XIV. 



PHORONIDEA.* 



Tubicolous, hermaphrodite Coelomata, with a tentaculated, horseshoe- 

 shaped lophophore, a dorsal anus, and one pair of nephridia. 



It is convenient in the present state of our knowledge to give 

 Phoronis the rank of an independent phylum of the animal kingdom. 

 It has been relegated by various naturalists to the Gephyrea, the 

 Polyzoa, the Brachiopoda, and even to the Enteropneusta, but to not 

 one of these groups are its affinities close enough to justify a phyletic 

 association. 



Phoronis is a coelomate animal with a vascular system, and an ecto- 

 derrnal nervous system. In the adult state it is sedentary, and inhabits 

 leathery tubes, to which particles of foreign matter, such as sand 



grains and sponge spicules, are 

 often found adhering (Fig. 437). 

 The animal can protrude the 

 anterior part of its body from 

 the opening of the tube, to 

 which it appears to be but 

 loosely attached. 



A number of individuals are 

 commonly associated together, 

 their tubes being twisted round 

 one another ; but their bodies are not connected in any way. We 

 are ignorant of the cause of this association of individuals ; it is 

 not known that they possess the power of budding at any stage of 

 their existence. The tube is secreted by the animal, very possibly 



' A^ ^ . H. Caldwell, "On the Structure, Development, and Affinities of 

 Phoronis," Proc. Hoy. Soc., 1882. Id., " Blastopore, Mesoderm, and Metameric 

 Segmentation," Q. J. M. S., 25, 1885. W. C. Mclntosh, "Phoronis Buskii," 

 Challenger Reports, 28, 1888. W. B. Benham, "The Anatomy of Phoronis 

 australis," Q. J. M. S., 30, 1889. E. Metschuikoff, "Ueb. d. Metamorphose 

 einiger Seethiere," Z.f. w. 2., 21, 1871. Id., " Vergl. Emb. Studien," Ibid., 37, 

 1882. 



FIG. 437. Three tubes of Phoronis psammophtta 

 (after Cori), natural size. 



