556 H. LYSTEE JAMESON, 



points from the condition that I find in Thalassema neptuni from the 

 British and Irish coasts. 



In Horst's (8) account aod figure of Hamingia I have no doubt 

 as to the homology of the crop (fig. 3 i.g) with that of Thalassema 

 neptuni. His figure and description of the oesophagus recall the 

 oesophagus and gizzard of the latter species. Very remarkable in 

 Hamingia is the length of the division of the alimentary canal which 

 lies between the crop and the vascular ring. In the three genera, 

 Echiurus, JBonellia and Hamingia the musculature of the intestine 

 resembles that of Thalassema neptuni. 



Naturally a comparison of the parts of the intestinal canal with 

 those of other Annelids and Invertebrates would be of little value, as 

 the digestive system is notoriously liable to undergo radical changes 

 in correlation with physiological ditïerentiation of its parts. I have 

 already referred to the specialization for a sand diet. The sketches 

 of the intestine of Sternaspis by Vejdovsky (18) and Rietsch (12 a) 

 cannot fail to recall that of the Echiurids. 



The question naturally presents itself to us — what is the nature 

 of the crop, and why does it present this highly glandular epithelium? 

 In Echiurus and Hamingia at any rate it agrees in the possession 

 of these singular longitudinal glandular ridges of epithelium. Without 

 observations on the living worm it would be rash to attribute to it a 

 special function, but I cannot help thinking that it may serve to 

 secrete the slime by means of which the particles of food and sand 

 are cemented into the characteristic food balls. As a support for this 

 I find the balls in all parts of the intestine, but never anterior to 

 the pre- intestinal constriction. 



On a comparison with Koren & Danielssen's sketch of Hamingia 

 (9, tab. 5, fig. 6) it appears to me that the division c must be the 

 crop, and we see here that immediately behind it numerous food balls 

 occur in the intestine. 



As to the significance of the inner longitudinal muscle fibres of the 

 intestine, I have observed that they are not continuous with those of the 

 fore-gut. and I can see no alternative to regarding them as a separate 

 structure developed inside the ordinary musculature. I cannot determine 

 from what tissue they take their origin, but it is interesting to note that 

 Eisig (4) has found in the Capitellidae (where a similar reversal of 

 the musculature takes place) what he believes to be epithelio-muscular 

 cells, i. e. muscular cells derived from, and still continuous with, the 

 endodermal epithelium, such as occur in the Coelenterata. 



