214 W. B. BENHAM. 



region, (2) pharynx, (3) oesophagus, (4) gizzard, (5) tubular 

 intestine, (6) sacculated intestine. 



The buccal region is always present, and is bounded pos- 

 teriorly by the circumpharyngeal nerve-collar : this region is 

 thinner-walled than the pharynx, and is eversible. 



The pharynx occupies some two to four of the following 

 somites : it is probable that the buccal region occupies always 

 the first and second somites/ and the pharynx the third to fifth ; 

 but as there are no septa in this region the pharynx fre- 

 quently appears more extensive than this: the thick muscular 

 wall is confined nearly entirely to the dorsal surface. 



The following region, up to the gizzard, is the oesophagus. 

 As will be readily seen by a glance at the diagrams, this region 

 is extremely variable in extent, according to the position of 

 the gizzard, which may lie in Somite v or in Somite xvii, or, 

 as in Monilig aster, still further back. 



The presence of two or more gizzards is by no means un- 

 common, and this leads to a repetition of the oesophagus. 

 How far the position of the gizzard is a generic characteristic 

 it is impossible to say: descriptions of the alimentary tract are 

 in most cases very brief, and it is well known that the gizzard 

 rarely lies opposite to the somite to which it belongs ; the 

 septa are very frequently pushed backwards, so that the 

 septum bounding a somite may, in the middle of the 

 body, come to lie at the level of a somite some little way 

 behind : in addition to this, the septa in the region of 

 the gizzard are not unusually very thin, and easily broken ; 

 and it thus comes about that, whereas the positions of the 

 various parts of the reproductive apparatus are carefully 

 noted, the real situation of the gizzard has sometimes been 

 less accurately observed. From the peculiar constancy in 

 position of the parts of the generative organs, and the varia- 

 bility in the position of the gizzard, I believe it will repay 

 future observers to turn their attention more particularly to 



1 In the diagrams I have rcpreseuted the buccal region as occupying the 

 first somite only : so little positive information is available on this point, that 

 I have not attempted to mark out the limits of the region accurately. 



