432 Dr. H. J. Hansen on the Morpliology of the 



44. COLEOPTEEA. — The mandibles, maxillfe, and labium 

 agree with the utmost exactness with those of the Orthoptera 

 in structure and relative position. A difference arises in 

 consequence of the fact that the hypopharynx is eitlier so 

 much reduced in size as to disappear, or, as seems to me more 

 probable, has become firmly attached to the inner side of the 

 labium, which on the whole becomes pressed upwards against 

 the underside of the head more closely than in the case of 

 Orthoptera; many peculiarities {e. g. m AleJoloniha) point to 

 the probability of the latter explanation. The maxillul^e are 

 entirely wanting. 



45. The hypopharynx is a freely projecting organ only in 

 the Thysanura, Orthoptera, and Diptera ; a]}parently we also 

 find it in the Rhynchota as a short free point (Wedde, and 

 my own observation in Nepn). It is often termed " tongue," 

 which may well be admissible, but is not very happy. On 

 the other hand, many authors frequently employ the term 

 ''tongue" in a very arbitrary and objectionable manner for 

 portions of the labium ; " paraglossa3," a term which should 

 be. entirely rejected, is used sometimes for portions of the 

 labium, and at others for parts of the maxillulse. 



AQ. The antennee in Insects are sometimes regarded as 

 homologous with the antennules and sometimes as homologous 

 with the antennae in Crustaceans. As an argument in favour 

 of the former supposition we have the fact that the antennse 

 of Insects, as also the antennules of Crustaceans, are inner- 

 vated from the deuterocerebrum (Viallanes) ; the second 

 theory is supported by two reasons. As has been demon- 

 strated with respect to both classes by a series of authors, the 

 rudiments of the antennge are postoral in position both in 

 Insects and in Crustaceans ; it is true that a single author has 

 stated the same thing with reference to the antennulse, but 

 this is certainly very much open to doubt. In the terrestrial 

 Amphipods {Orchestia) the first pair of antennae, the an- 

 tennules, have become very short, and in the most charac- 

 teristic land-Isopods {ArmadiUidium, Armadillo^ Tylos^ 

 Sys'ijastus) they have become extraordinarily small and are 

 reduced even to the point of disappearance, while the second 

 pair of antennse are well developed. 



47. Upon the mandibles of certain Coleoptera and larvajof 

 several species of Ephemeridas I have found a well-developed 

 lacinia mobilis. 



48. How far the embryonic provisional lobes which have 

 been found by diff'erent authors in several of the higher orders 

 of Insects (and with respect to which Korschelt and Heider 

 write on p. 793 of their text-book : " This lower-lip-forma- 



