194 FOURTH REPORT — 1834. 



and Entomostraca of this last author are retained as primary 

 divisions, and the former is still divided into the two secondary 

 groups of Podophthalma and Edriophthalma ; but the groups 

 next in succession are the same as Latreille's orders. At the 

 satne time there is a slight modification of these orders among 

 the Entomostraca . 



Risso, who has paid considerable attention to the Crustacea, 

 adopts, in his Hist. Nat. de I'Eur. Merid., published in 1826*, 

 nearly the same arrangement as that of Desmarest. 



The most important, as well as most recent, additions which 

 have been made to our knowledge of the Crustacea are due to 

 the researches of MM. Audouin and Edwards, who have for some 

 years back, the latter gentleman more especially, given particular 

 attention to this class of animals. Indeed it is impossible to 

 speak too highly of their labours in this department. Bearing 

 in mind the close connexion which subsists between zoology 

 properly so called, and comparative anatomy and physiology, 

 they have commenced by studying closely the internal as well as 

 external organization of the Crustacea, before proceeding to in- 

 vestigate their natural affinities. The results of their researches 

 on this branch of the subject are contained in a series of me- 

 moirs published in the Annales des Sciences, of which anylengthr 

 ened analysis here would lead too much into anatomical details. 

 It may be just stated, that in their first two memoirs, published 

 in 1827t, they have treated of the circulation of the blood, con- 

 cerning the true course of which there prevailed before much 

 difference of opinion. They have determined with accuracy the 

 exact method in which the circulation is effected, and found it 

 to be in some respects analogous to that which is known to pre- 

 vail in the molluscous animals^. In a third memoir, published 

 in 1 828 §, they have entered into considerable details with respect 



* The Crustacea are contained in the fifth volume. Risso had published 

 some years previously a work entitled, Histoire Naturelle des Crtistaces det 

 Environs de Nice, 8vo, Paris, 1816. 



t Ann. des Scien., torn. xi. 



J Two memoirs on the circulation of the Crustacea have been also published 

 in Germany by M. Lund, the one prior, the other subsequent, to those of Au- 

 douin and Edwards. In the first {his, 1825,) the author observes that he has 

 never been able to discover the slightest trace of veins in the Crustacea, which 

 he thinks are without them, and in consequence deprived of a complete circu- 

 lation. In the second (Isis, 1829,) he confines himself to some remarks on the 

 researches of Audoxiin and Edwards, who have arrived at such difl^erent results 

 from himself. He allows that they have discovered a system analogous to the 

 venous system of the Vertebrata and Mollusca, but does not agree with them as 

 to a near affinity between the Crustacea and Mollusca in regard to their circula- 

 tory organ*; 



§ Ann., torn. xiv. p. 77j 



