TYPHLORHYNCHUS NANUS. 641 



This consists of a reticulum of delicate fibrillar protoplasm 

 containing round finely granular nuclei ; the protoplasm is 

 without cell limits^ and the nuclei are few and widely scattered. 

 Most of the body organs, e.g. yolk glands, penis, etc., lie in 

 perfectly definite spaces in this parenchyma, but in two 

 cases, viz. the gut wall and the bursa seminalis, this is not 

 so. The liniug of the gut space consists of protoplasm 

 without cell limits, of precisely the same character as that 

 of the parenchyma, and it is not marked off from the latter 

 in any way. The only characters which serve to distinguish 

 the gut wall (endoderm) from the parenchyma are, firstly, the 

 nuclei, which in the endoderm are oval, and contain coarse 

 darkly staining chromatin granules (fig. 7,Nuc.), whilst those 

 of the parenchyma, as stated above, are round and finely 

 granular (fig. 7, P. N.) ; and secondly, the presence in the 

 endoderm protoplasm of numbers of fine granules, which are 

 probably food granules, but these only disappear gradually 

 in passing from the endoderm to the parenchyma. 



In the case of the bursa seminalis the protoplasm forming 

 its walls, though denser and more hyaline than the general 

 parenchyma protoplasm, nevertheless merges quite imper- 

 ceptibly into it. 



Owing to the spaciousness of the enteron and the size of 

 the yolk glands in the middle regions of the body, the 

 parenchyma in those regions is much reduced. 



In the proboscis the parenchyma is densest immediately 

 under the body- wall; below this it is spongy and scarcely 

 distinguishable, especially towards the tip of the proboscis. 



Alimentary Canal. — The mouth opens on the mid-venti-al 

 line just behind the constriction at the base of the proboscis. As 

 already stated, there is a sphincter muscle arrangement around 

 the mouth opening, developed from the muscles of the body- 

 wall, most probably from the outer circular layer, but possibly 

 from both ; my sections do not bring this point out clearly. 



The mouth opens into the pharyngeal pouch ("Pharyngeal- 

 tacshe," von Graff j. This pouch is at first narrow, but as it 

 passes dorsally it widens into a chamber of small size, into 



