P(ECILOSTOMA. 27 



secondly, that I sometimes, as, for instance, in Licho- 

 molgus albens, found a small longitudinal, semi-pipe- 

 formed depression or groove exactly at the place where 

 the sipho of, for instance, Dyspontius and Ascomyzon is 

 inserted, and which I therefore considered to indicate 

 the place where the sipho and mandibles ought to be 

 found if any mandibles existed ; and thirdly and chiefly, 

 that sometimes, as in the genus Lichomolgus, the so- 

 called ' maxillae ' are fixed on the ' mandibles ' (quite 

 as an ordinary palpus is fixed on a mandible or a 

 maxilla), and directed from the oral aperture, a cir- 

 cumstance with which I could find nothing analogous 

 in the class Crustacea, supposing Glaus' ' mandibles ' 

 really to be mandibles." 



The greatest difficulty which besets the discussion 

 of this question is the minuteness of the mouth-organs 

 in these animals, and the liability to displacement or 

 mutilation of the various parts in conducting a dissec- 

 tion, so that the organs of one and the same species 

 will often present very different appearances in differ- 

 ent preparations of the animal. There can be no 

 doubt, however, that the fact so strongly insisted on 

 by M. Thorell, that of the coalescence, in Lichomolgus, 

 of the maxilla and mandible (or maxilla and palp) does 

 really exist : the question remains, What is this palp- 

 like organ ? In appearance it is not unlike the poorly- 

 developed mandible- or maxilla-palp of many Grnathos- 

 toma, but it is also much like a single branch of such 

 a maxilla as we find in the genus Cyclopicera or Arto- 

 trogus, so that not much can be learned by comparison 

 of structure only. The point next to be considered is 



