160 Marine Investigations in South Africa. Vol. V. 



branches, but these do not pass into " circuiai- " vessels only, but 

 lead by a large vessel (often swollen up into a large cavity full of 

 blood corpuscles) directly into the two branches of the efferent 

 vessel, so as to effect a direct communication between afferent and 

 efferent vessels. 



This was confirmed by observation on the circulation in the 

 living animal as given below, where the circulation is more fully 

 discussed. 



Affinities of P. capensis. — The species seem nearest to P. 

 hippocrepia. It differs from specimens of this species which I have 

 examined in the structure of the transverse septa, as already 

 indicated, and in the number of tentacles. The latter characteristic 

 is, however, very variable, and the value of the former as a specific 

 characteristic is not yet proved, and it is by no means certain that 

 the forms are distinct. 



The wide geographical separation of the species can reasonably 

 be accounted for by the habits and modes of occurrence of the 

 animals as here described. If they can be conveyed through a 

 pump, a long pipe, with a fall of about a foot into a tank of water, 

 and become aftixed to a stone, it is more than probable that they 

 will lodge in the material which accumulates on ships' bottoms, or 

 floating pieces of wood, and be carried great distances in this way. 



Obsebvations on Behaviour and Habits of Phoronis capensis. 



There is still some considerable doubt on many points connected 

 with the general habits and certain physiological phenomena of 

 Phoronis. Its formation of what might be called " pseudo-colonies," 

 in which there is apparently no co-operation or advantage to its 

 individual members ; how the animal apparently penetrates solid 

 limestone ; how the tube is formed ; how food is ingested ; function 

 of the " lophophoral organ" and of epistome ; nature of sense 

 organs, if any ; whether the movement of the blood is real circula- 

 tion or merely oscillation — these and other points still remain 

 somewhat obscure. 



The following notes are based on observations for a year on a 

 " colony," and on specimens occasionally procured by dredging, and 

 also on repeated observations made under the microscope on speci- 

 mens living in as normal conditions as possible. For convenience, 

 I have arranged these under the following heads :— 



(a) Mode of occurrence, formation of tube, boring (?), colony 

 formation. 



(b) Tentacles, muscular and ciliary movements. 



