168 Transactions of the South African Philosophical Society. 



epistome escapes by this "gap" into the inner circle as has been 

 suggested (Masterman (6)). 



It is merely the point of origin of the tentacles, which in this 

 region are of all sizes ; two sometimes scarcely projecting have been 

 seen at each side touching each other across the " gap," and follow- 

 ing these 5 or 6 on each side rapidly increasing in length till they 

 join the fully developed tentacles of the inner circle. These smaller 

 tentacles on each side often overlap at their tips, preventing any 

 wide opening between the regions of the inhalent and exhalent 

 currents. 



The contraction of these small tentacles and of the tissue in the 

 neighbourhood of the gap, along with the approximation of the 

 tentacles in preserved material, doubtless bring about the appearance 

 of a large gap in sections of this region. 



The epistome could be readily observed in the living animal in 

 certain positions. In contrast to the other organs of the body it 

 showed a constant and active movement. This occurred at its 

 free edge. Observations were, of course, only possible when the 

 lophophore was fully extended. In this condition the epistome 

 was usually held back against the inner circle of tentacles, the 

 mouth being widely open. Occasionally, however, the epistome 

 descended over the mouth, closing or partly closing it. Various 

 suggestions have been made as to its action, directing the currents of 

 water (Masterman (6)), preventing a direct passage between mouth 

 and anus through the lophophoral gap (Benham (2) ). These, though 

 quite justifiable deductions from a study of sections, do not seem 

 probable in view of what has been noted above with regard to the 

 behaviour of the animal in the living condition. So far as observa- 

 tions went, the function appeared to be the obvious one of closing 

 the mouth, and its lateral extension on each side ; it is doubtless also 

 partly sensory. 



Circulation. — Though the closed vascular system with red blood of 

 Phoronis is one of its most striking characteristics, there is still some 

 doubt as to whether there is actual circulation or merely oscillation 

 of the blood. This is probably to be accounted for by the difficulty 

 in obtaining accurate observation of the course of the blood. In a 

 recent paper Enriques (5) describes a unique type of circula- 

 tion which he has observed in Phoronis psamniophila. He was 

 enabled to examine the circulation microscopically by removing the 

 animal from its tube by a method which he considers would not 

 injure the animal to such an extent as to upset its normal circula- 

 tion. Briefly, his conclusions are that there is an oscillatory 

 movement of the blood plasma, and that, during this process, the 



