STRUCTURE OF A GENUS OF OLIGOCH^TA. 5 



The cesophagus commences as a very narrow tube; this region is pressed up against 

 the first thick mesentery, which separates segments V and VI. Its direction here is 

 ventro dorsal; it must, however, in my opinion, be regarded as belonging to the Vth 

 segment. In the Vlth segment the oesophagus broadens out considerably, acquiring a 

 calibre about twice as great as that which it possessed in segment V. The cesophagus 

 here is quite as wide as the gizzard; this wide region of the cesophagus occupies seven 

 segments — VI-XII. (inclusive). I could not find any evidence of the existence of 

 calciferous glands. But as these structures appear to fluctuate very considerably in 

 their size at different seasons of the year, it is possible that I have overlooked rudiments 

 which might at stated times become large and important glands. 



Gizzard. — Unless there is a very unusual degree of variation in the number and 

 position of the gizzards, my earlier account [1, p. 94] is wrong. I then stated that M. 

 Barwelli is distinguished from M. Deshayesi by the absence of a gizzard in the Vlth 

 segment, but agrees with that species in the presence of " four oval nacreous-looking 

 dilatations of the cesophagus close to its junction with the intestine." 



Longitudinal sections (of two individuals) show plainly that there are only three 

 gizzards, placed in consecutive segments, and each occupying a segment near to the 

 junction between the cesophagus and the intestine. In confirmation of this, a specimen 

 (unfortunately the last which I possess), dissected in order to compare it with the longi- 

 tudinal section, showed plainly three gizzards situated close together and in consecutive 

 segments. I feel therefore pretty sure that I must in my earlier account have mistaken 

 for an additional gizzard a swelling of the cesophagus. The probability of this is increased 

 by Bourne's [6, p. 672] observation, that in M. ruber "in segments X, XI, and XII, 

 there were soft- walled swellings of the intestine -looking like gizzard, only not muscular." 

 The segments occupied by the gizzards appear to be XIV, XV, and XVI. This state- 

 ment is made on the strength of the dissected individual, and one of the two that were 

 cut into longitudinal sections ; the second specimen which I prepared in a series of sections 

 did not show very plainly the exact position of the gizzards. 



To the naked eye the gizzards present a longitudinally striated appearance, as is 

 commonly the case with this organ. The striation appears to be chiefly due to the longi- 

 tudinal direction of the blood-vessels upon the surface of the gizzard ; each gizzard, on 

 account of its peculiarly compressed shape and this longitudinal striation, has a most 

 extraordinary resemblance to an onion. This is illustrated in fig. 5 of the Plate. 



Fig. 10 illustrates a diagrammatic longitudinal section through the fifteen anterior 

 segments, to show the number of segments occupied by the successive regions of the gut. 

 It is not meant to illustrate the proportionate lengths of these different regions ; for 

 example, the pharynx appears much longer than in the figure, while the cesophagus is 

 much shorter. This is brought about by the increased space available in segments IV 

 and V, due to the course of the septum separating segments V and VI; this same 

 structural peculiarity reduces the space occupied by the cesophagus. 



