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very elongated epitbelial cells aud as the buccal cavity is nothing 

 bui au iuvagiuatiou of the anterior part of the body, it is clear 

 thiit the three kinds of glauds eau be considered as homolosra 

 aud that tliey have obtaiued their special functious afterwards. 



The orifices of the prostomialglauds resem bic those of the sali- 

 vary glauds at the side of the jaw ; ouly those prostoruial glands 

 occur iu a far greates uumber. The glandular ducts or secreting 

 ducts are so uumerous iu some places of the sucker that only 

 a couple of epithelium cells are fouud between two ducts. 



Under the epithelium of the skin the pigment cells are situa- 

 ted , which are placed iu particularly long rows and form a net- 

 work which seuds its ramifications everywhere. 



Upou each of the three oesophageal folds of the Gnathobdel- 

 lidae we may observe by minute examiuation of the buccal cavity 

 a small tumefaction , which possesses more or less teeth or den- 

 ticules on its convex edge. The largest dimension of this tume- 

 faction or jaw lies iu the longitudinal direction of the folds. 

 Blainville proposes to call those orgaus »mamelons dentifères" 

 aud there is certaiuly somethiug to say in favour of his propp- 

 sition ; the name jaw however is commonly used and I will 

 therefore keep this term. 



Before 1 go on iu describiug the structure of the jaw, I will 

 speak about the salivary glauds and their secretory ducts, the 

 latter forming for some part the body of the jaw. 



Though sectious may give a good idea about the structure of the 

 liead and of the jaw in general, they do not suffice for studying 

 the exact form of the glands and their secretory ducts. There- 

 fore I proceeded as follows : 1 separated with oue blow of the 

 scissors the head of the living aniraal, theu I opened the head 

 longitudiually aud prepared the jaw with the neighboring glands. 

 This was put iu Na Cl solutiou of 0,5 procent aud examined 

 carefully. 



The glands are pearshaped and fiUed with a very fine granular 

 mass. The granules in the ducts are quite the same as those , 

 which are fouud iu the glaud. The membrane of these gland- 



