(176) 



EEFEEENCES. 



1) Beneden, p. T. Van. Note sur un Annelide cephalobranche sans soies, 

 designe sous lo nom de Crepina. Ann. Sc. Nat. (Zool.) 4^ s^rie, vol. x., 

 1858. 



(2) Benham, W. B. The Anatomy of Thoroiiis Australis. Quart. Journ. Micr. 



Sc, N.S., vol. XXX., 1889. 



(3) Caldwell, W. H. Preliminary Note on the Structure, Development, and 



Affinities of Thormiis. Proc. Roy. Soc., No. 222, 1882. 



(4) Gobi, I. Inaugural Dissertation. Prague, 1889. 



(5) Enriques, p. Atti R. Accad. Lincei, Roma, xiv., 1905. 



(6) Masterman, H. On the Diplochorda. Quart. Journ. Micr. Sc, vol. xliii., 



Part 2, N.S. 



(7) McIntosh, W. C. Report on Plwrunis Buskii. Challenger Reports, vol. 



xxvii., 1888. 



(8) Selys Longchamps, M. Ueber Phoronis und Actinotrocha bei Helgoland, 



Wiss. Meeresunt. Neue folge. Sechster Band. Abtejlung Helgoland. 

 Heft 1. 



EXPLANATION OP PLATES XVI., XVII. 



Fig. 1. — Plioronis capensis in nearly complete expansion. The eggs are 

 indicated in the inner circle of tentacles, the jaculatory movement of tentacles 

 by a bent tentacle on the left, the nerve ring by white lines, and the digestive 

 tract by a longitudinal white band. 



Fig. 2. — Phoronopsis albomaculata, viewed from above (from a photograph of 

 the living animal in complete expansion). 



Fig. 3. — Longitudinal section of Phoronopsis albomaculata (specimen B), 

 showing fold of epidermis and nerve ring. hi. Blood-vessel, bt. Basement tissue. 

 ep. Epidermis of body, ep' . Modified epidermis of fold. eps. Epistome. int. 

 Tangential section of wall of intestine, lo. Lophophoral organ, n. Nervous 

 tissue, nepli. Section of duct of nephridium. 



Fig. 4. — Enlarged view of nerve ring with epidermal fold shown in fig. 3. 

 bt. Basement tissue, coe. Coelomic epithelium, ep. Epidermis of body, ep' . 

 Modified epidermis of fold. n. Nervous tissue, neph. Section of duct of 

 nephridium. ts. Transverse septum. 



Fig. 5. — Transverse section of Plioro^iopsis albomaculata (specimen A). The 

 section is in reality oblique, as the organs of the left side were at a lower level 

 than those of the right. Figuring as in Fig. 4 with the addition of a. Anus. 

 m. Mouth, nep' . Cells of internal opening of nephridium. 



Fig. 6. — Median longitudinal section of Phoronis capensis. b.t. Basement 

 tissue, eps. Epistome. m. Mouth, n.e. Sub-epidermal nerve tissue of nerve 

 ring. n.e'. Nerve tissue near mouth (organ of taste'.'). oe. CEsophagus. 

 t. Tentacle. 



