342 FUNAFUTI ATOLL. 



Plate xxii., fig. 11, represents a section taken shortly behind the 

 last pair of gill pockets, and it will be seen that we have here the 

 same general external form of the body as was described above for 

 the posterior portion of the branchial region. In other words, the 

 median dorsal projection there found continues back into the 

 anterior portion of the genital region, and is bounded laterally by 

 deep grooves, the continuations of the branchial grooves, now, 

 however, much deeper and narrower below. Beneath these grooves, 

 the longitudinal musculature is absent. 



Just as the median dorsal projection in the posterior branchial 

 region lodged the branchial canal, so here it lodges a remarkable 

 thick- walled dorsal division of the alimentary canal (fig. 11, idv.) 

 which is joined by a short, laterally compressed stalk, to a ventral 

 division of the intestine, lined by ordinary intestinal epithelial 

 cells (fig. 11, i.). The dorsal division possesses a small lumen 

 which opens by a narrow slit-like cleft in the connecting stalk, 

 into the broad and dorso-ventrally compressed lumen of the 

 ventral division. 



At its anterior end the dorsal diverticulum projects forwards 

 over the last pair of gill pockets as a very short, free, blindly- 

 ending tube, the lumen of the diverticulum opening below into 

 that of the branchial canal. The lumen of the ventral division 

 of the intestine is the direct continuation of the cesophageal canal 

 of the branchial region. 



Posteriorly the slit-like canal of commnnication between the 

 dorsal and ventral divisions of the intestine gradually widens out, 

 and at the same time the dorso-lateral corners of the ventral 

 division of the gut extend inwards mesially, giving rise to two 

 prominent folds, one on each side of the opening between the two 

 divisions. These two folds eventually become free and end shortly 

 behind the point of complete merging of the dorsal division into 

 the ordinary gut. It has also to be mentioned that posteriorly 

 the branchial grooves by the fusion of the mid-portions of their 

 opposite walls, form two very short and blindly-ending canals 

 which pass back one on each side in the trunk crelom, alongside 

 the dorsal diverticulum. 



This dorsal division of the gut is lined by a very deeply staining 

 and slightly folded epithelium measuring up to '25 mm. in thick- 

 ness. The epithelium is composed of long, narrow cells closely 

 packed together, with small rod- or spindle-shaped nuclei. The 

 cell-protoplasm contains large numbers of small granules staining 

 a dull red with eosin. Below the thin cuticular covering of the 

 epithelium there occur very numerous gland cells, which open 

 freely into the lumen of the diverticulum. 



As has already been mentioned, Spengel has described the 

 occurrence of a similar subdivision of the gut canal just behind 



