General Structure of Phoronis Pacifica 
Torrey 
RUTH LEDIG 
Phoronis lives in tubes formed by particles of sand and small pebbles which are 
held together very firmly by a secretion from the body. These tubes are entirely 
separate from each other. In preserving the animals for sections the tubes were usually 
removed from the animals before fixation. The usual picric or mercuric fixing reagents 
seemed to give good results. After sectioning or before, a carmine or hematoxylin 
stain was used; the latter gave the best results, followed with eosin. The animals 
are so small and delicate that it was necessary to study their anatomy by means of 
serial sections. 
In Phoronis the buccal and anal openings are both in the anterior end of the 
animal. The head end has two lopophore organs bearing numerous tentacles arranged 
spirally. The digestive tract is U shaped. This species varies in length, based on the 
material at hand it is from one to two and one-half inches in length. 
The vascular system consists of a circular ring of the blood vessel about the 
esophagus. From this ring vessels run into each tentacle and one vessel follows and is 
parallel with the digestive tract. Opposite to this vessel is one returning the blood to 
the circumesophageal ring. 
The nervous system consists of a ganglion between the anal and the mouth 
epening, It is made of modified surface cells. From this ganglion a circle of nervous 
tissue extends about the esophagus and from this a single unsymmetrical nerve or 
sense organ runs the length of the body in the epithelium of the body wall. 
Two nephridia are found, each of which is situated near the surface equally 
distant from the anal opening. 
Phoronis pacifica has both testis and ovary in the same individual. 
Further details of structure are shown in the figures. 
BIBLIOGRAPHY 
Andrews, E. A. 1890 
Phoronis architecta. é 
Ann. mag. nat. hist. 6th. ser. vol. v. 
Benham, W. B. 1888 
Anatomy of Phoronis australis. Quart. jour. mic. soc. xxx. 
Cori, G. J. 1890 
Untersuchungen ueber die Anatomie und Histologie der Gattung Phoronis. 
Zeit. f. wiss. Zool. li. 
Delage, Y. et Herouard, E. 1897 
Traite zoologie concrete. T. vy. Les Vermidiens, Paris. 
M'Intosh, W.C. 1888 
Report on Phoronis buskii. : 
Voyage of H. M. S. Challenger Ixxv. 
Torrey, H. B. 1901 
On Phoronis pacifica Sp. Nov. 
Biol. bul. vol. ii, no. 6. 
(Contribution from the Zoological Laboratory of Pomona College) 
