408 ON THE OltDJiltS 



am not only still unable to refer the construction of the 

 mouth of his Apiropoda to any one type, but cannot even 

 form an abstract idea of the organs of manducation in 

 the circles of Crustacea, of Arachnida, or Ametabola, 

 taking each class separately. 



M. Latreille indeed, in his late Mtmoire, read before 

 the Institute, on the formation of the Wings of Insects 

 and their external organization considered with reference 

 to that of the Arachnida and Crustacea, has attempted to 

 remedy by a new theory the anomalies so apparent in that 

 of M. Savigny ; but he has only made more manifest the 

 extreme difficulty of the investigation, and the futility as 

 yet of all endeavours to surmount it. This Mtmoire of 

 M. Latreille, although unsuccessful in its attempts to- 

 wards a general theory of the mouth, is nevertheless full of 

 most interesting speculations, in the illustration of which by 

 anatomy every friend to natural science must be gratified in 

 learning that he is now busily employed. His opinion with 

 respect to the antenna? of Arachnida has already been dis- 

 cussed, and, if correct, goes a great way towards our ob- 

 taining a definite notion of the type of the Annulosa. 

 But, in addition to this, M. Latreille makes a daring at- 

 tempt to substantiate the accuracy of an hypothesis which 

 I believe, with the exception of the late M. Jurine's ap- 

 proach towards it, is quite new and entirely his own. 

 He argues, that as the Vertebrated animals offer so striking 

 a correspondence in their organs of locomotion, the pro- 

 bability from analogy is, that Nature in the structure of 

 the Annulosa may, notwithstanding her deceitful exterior, 

 be found on accurate examination to be equally consistent 

 with herself. Now, to prove the justness of this position, 

 he states that in some species of Caligus he has observed 

 the feet to be fan-shaped, divided at the extremity into 



