N0TK8 ON AOTTNOTROOHA. 483 



along the bottom of the vessel in which it is kept, performing 

 a sloAv pirouette in its course. Probably the sense papilla 

 which is placed on the ventral surface of the hood, and which 

 would thus come in contact with the ground, is the organ by 

 means of which the larva feels its ground before settling- 

 down for the rest of its life. 



In conclusion it may be added that if Actinotrocha is 

 related to the Chordata at all, as the presence of three 

 divisions of the body with their corresponding cavities, of 

 collar nephridia, of a dorsal diverticulum of the anterior 

 part of the gut, and of a dorsal tubular nerve-ganglion 

 renders probable, the absence of such important struc- 

 tures as the gill-slits, and of the proboscis pores shows 

 that the relationship is to be traced through a form like 

 Rhabdopleura. 



EXPLANATION OP PLA'PP 26, 



Illustrating Mr. K. Eamunni Menon's paper entitled "Notes 

 on Actinotrocha.'^ 



TAst of AbbreviatioJis. 



an. Anus. an. bd. Perianal band, bl.-c. Blood-corpuscles, bl.-v. blood- 

 vessel, c. c. Collar cavity, c. ep. Somatopleure. c. ep^. Splanclinopleure 

 round oesophaj^us. c. ep^^. Splanchno|)cure round stoniacli. d. bl.-v. Dorsal 

 blood-vessel, ep. Epistome, M. Preoral lobe. M. e. Preoral caviij. m. 

 Mouth. })ies. Mesentery between preoral cavity and collar cavity. mesK 

 Mesentery between collar cavity and trunk cavity. 31. nep. Posterior nephri- 

 dium (Mastcrnian). nep. Nepliridiuni. oes. (Esophagus. reel. Rectum. 

 lent. Tentacle, tr. c. Trunk cavity. Ir. w. body-wall of the trunk region. 

 vac. eel. Vacuolated ectoderm. 



Pig. 1. — Horizontal section of the anterior part of a newly metamorpliosed 

 Phoronis. 



Pigs. 2 — 4. — Sagittal section of the anterior end of young l^horonis, to show 

 the development of the epistome. 



