548 s. LYSTEIl JAMESON, 



Rietsch's figure and description of the intestine and fore-gut 

 of Thalassema neptuni and their relations to the blood vessels differ 

 so much from my observations that I am led to conclude either that 

 owing to lack of material he was unable to gain a clear idea of the 

 relations of parts, or that his jMarseilles Thalassema is not Th. neptuni, 

 but another species. 



The gizzard (9) goes suddenly over into the crop (cr) which 

 in Thalassema neptuni, as in Echiurus, is embraced at its posterior 

 end by the blood vascular ring. This region is usually 4—5 mm long, 

 with thin walls which in surface view present a longitudinally striated 

 appearance (Fig. 12 cr), which is due to the nature of the epithelium. 

 This forms a number of wavy yellowish white glandular ridges or folds 

 the structure of which will be described immediately. Along the 

 dorsal surface lies the dorsal blood vessel, in the substance of the 

 dorsal mesentery, by which it is bound to the crop. Posteriorly this 

 vessel goes over into the two limbs of the neuro-intestinal anastomosis 

 which embrace the hinder end of the crop (see Fig, 12), Like the 

 gizzard the crop lies somewhat to the left of the nerve chord. It often 

 appears to be somewhat wider than the gizzard , but this is not 

 always so. At the point of origin of the crop the narrow lumen of 

 the gizzard suddenly widens out, and the wall becomes thin, the 

 simple epithehum of the gizzard goes over into the highly complicated 

 epithelium of the crop, a sudden and marked transition, seen as 

 well in sections as in the dissected worm. At the hinder end of the 

 crop, the transition from crop to intestine is even more sudden owing 

 to the strong constriction and the change in the musculature, as well 

 as the change in the nature of the epithelium. The intestine, 

 behind this constriction, is immediately marked by the presence 

 of the ciliated groove. The musculature of the crop consists, as in 

 the preceding divisions , of an outer layer of longitudinal muscles 

 (Fig. 17 l.m) and an inner layer of circular muscles (cm). As a 

 rule both are very weakly developed, one or two strata of fibres in 

 each layer. 



As above stated, on examining a dissected Thalassema, the crop 

 is marked by the presence of about twelve somewhat sinuous white 

 bands. These prove on section to be longitudinal ridges of highly 

 specialized glandular epithelium, separated by deep valleys in which 

 the cells are simpler. 



The relations of the cells in these ridges are very complicated. 

 The immense development of basal cells and bottle-shaped gland cells, 



