6 Transactions of the Society. 



constricted by a circular muscular arrangement at the point where 

 it enters the ventriculus, forming a very perfect valve, which 

 prevents any food material from returning from the ventriculus to 

 the oesophagus ; this may often be seen very well by the air-bubble, 

 which, carried by the liquid in which it is floating, may be observed 

 to pass down from the oesophagus to the ventriculus, but it is always 

 stopped at the valve whenever it has a tendency to return. The 

 oesophagus enters the ventriculus about the centre of the anterior 

 end, which possibly it may not be proper to call cardiac in a 

 creature which is not known to possess any heart. 



The ventriculus is the largest and most important portion of 

 the canal ; it is a wide sac, occupying from half to about two-thirds 

 of the length of the abdomen, near the dorsal surface (plate I. figs. 

 1, 2, 3, 4, 6), In Nothrus theleproctus the sac is of a shape 

 approaching pyriform, the narrower end being the anterior one, 

 this however is rounded, although smaller than the hinder part ; 

 the posterior end has a tendency to a blunt median point. The 

 walls of this viscus are thick and muscular, more so than any other 

 part of the canal except the rectum, and it is here that digestion 

 doubtless chiefly takes place, a food mass may, most frequently, be 

 seen occupying the pyloric portion. From the widest part of the 

 ventriculus, i. e. about two-thirds of the length from the anterior end, 

 a large csecal diverticulum arises on each side, and, in the present 

 species, after standing outward (laterally) so as to form a shoulder, 

 proceeds almost straight backward. These diverticula are longer 

 than the ventriculus itself, often more than half as long again, and 

 nearly half its diameter ; they are of almost even size throughout, 

 so that they present a sausage-like appearance; theu' posterior 

 ends are rounded. 



There are probably greater differences between the ventriculus 

 and csecal apj)endages in different species and genera of the family 

 than are found in any other part of the canal ; this is especially true 

 of the size and form of the caeca. In Hoplophora magna they 

 have become very small in proportion to the ventriculus, which is 

 widest anteriorly, and prolonged almost to a point behind. The 

 caeca are globular, and are attached to the ventriculus by short 

 peduncles (plate I. tig. 2, (^). I mention this species, as Nicolet 

 figures it without caeca, which is not correct in the specimens which 

 I have dissected. In the case of Dampens clavipes, the caeca are 

 not any longer distinctly visible, but are mere enlargements of the 

 outer posterior angles of the ventriculus. Dammus geniculatus is 

 an intermediate form in this respect. 



Nicolet treats the caeca as being simply diverticula of the 

 stomach, without any special ofl&ce, and this probably may be the 

 most obvious and natural suggestion ; as far, however, as my own 

 judgment goes, I doubt the correctness of the view. In the very 



