786 PROFESSOR J. STEPHENSON ON 



forced into the ventricle, and this contracting in its turn passes the air and water into 

 the intestine, whence they are expelled either tlirough the proboscis or anus. The same 

 was observed in Kefersteinia cirrata. 



Malaqdin (30), like de St Joseph, never saw the ventricular cseca of Syllids distended 

 with air, not even when the animals were taken floating ; accordingly he too denies 

 Eisig's conclusion that they can function as hydrostatic organs. He describes the 

 suckino- action of the proventriculus (the cylindrical portion of the alimentary canal 

 in front of the ventricular cjeca) ; this is peristaltic in nature, a progressive diastole 

 from front to back being followed by a progressive systole. The animal frequently 

 rejects the water which it has taken in in too large quantity by similar series of 

 contractions executed in the reverse direction. 



The cfeca cannot be considered as special glands, since the epithelium, though 

 secretory, has the same structure as that of the anterior intestine ; their secretory 

 function is thus identical with that of this portion of the alimentary tube, and in no 

 way peculiar. As has been seen, they are not swim-bladders ; they must therefore be 

 considered as reservoirs to contain the surplus water" taken in by the mouth ; when 

 they are absent, the anterior portion of the intestine serves this purpose. 



Eespiration is thus not solely cutaneous ; the swallowed water is an indication of 

 the respiratory importance of the intestinal epithelium. This, however, must not be 

 exaggerated ; the ventricular cseca, when they exist, being reservoirs of water, may play 

 a more important part than the intestine in the discharge of the respiratory function. 



ScHAEPPi (41), after noting that Oj>helia radiata has no gills in the anterior part of 

 its body, describes the whole anterior portion of the gut — the oesophagus and especially 

 the stomach — as being characterised by an extremely rich folding ; the gut sinus 

 extends into these folds. " Now it is known that especially in mud-dwelling worms 

 alimentary respiration is an essential complement to cutaneous and branchial (or 

 specialised cutaneous) respiration ; and I am convinced that this factor is not to be 

 neglected in Ophelia, where over a large region the lumen of the gut is reduced by this 

 folding to a labyrinth of narrow clefts." He concludes that the blood is oxidised in 

 these folds ; the oxidation process, which is carried out in the hinder region of the 

 body by gills, is thus eflected in the anterior by the gut. Since nothing is said about 

 the mode of introduction of respiratory water into the oesophagus and stomach, it would 

 .seem that Schaeppi conceives it as entering at the mouth. 



Salensky (40) describes the pharyngeal sacs oi Polydora (Spionid) as five symmetrical 

 evaginations of the wall of the alimentary canal, resembling in their manner of formation 

 the gill-pouches of Enteropneusta and Chordata, with which they are probably 

 homologous. These pouches are found also in Saccocirrns and Poli/goixlius. It is not 

 stated that they are homologous with the T-shaped glands of Syllids ; and nothing is 

 said regarding their physiological value. 



BouNHiOL (5, 6, 7) is acquainted with the respiratory function of the anterior part 

 of the alimentary canal in Syllids ; his papers are mainly concerned with quantifaitive 



