666 Zweite Sitzung der sechsten Sektion. 



specimens of Arthropleura defends strongly the isopodan affinities 

 of that genus and of Praearciurus. In discussing the relationship 

 of Arthropleura with Oxyuropoda, Andree accepts, on the whole, 

 the interpretations given in the original description of the latter 

 genus, and dwells on the importance of its study as calculated 

 to elucidate the nature and affinities of the primitive Iso- 

 poda. 



We are able then to claim with conf idence a high geological 

 antiquity for the Isopod Crustäcea. And the same Devonian 

 formation which has yielded Oxyuropoda has also yielded the 

 oldest remains of insects known to us. This suggests a few re- 

 marks on the possibility of a near relationship between the Crustä- 

 cea and the Insecta. It is now seventeen years since Hansen 

 argued 1 ) for such a relationship, pointing out the close resem- 

 blance of the thysanuran mandible to the mandible of the Cumacea, 

 the existence in the Apterygote insects of a pair of maxillulae 

 (comparable to the first maxillae of Crustaceans) behind the 

 mandibles, the frequent presence, in both classes, of a segment 

 primitively belonging to the trunk (labial or maxillipedal segment) 

 in close association with the head, and the exact numerical corre- 

 spondence in the segmentation of the body between a primitive 

 insect and a malacostracan. These cofrespondences may seem 

 fanciful to those zoologists, who believe in a great gap between 

 „tracheate" and „branchiate" arthropods, but signs are not 

 wanting, that in the near future Hansens work will receive 

 its deserved recognition. In England, Lankester accepts the 

 view that the Insecta are related not merely to the Crustäcea 

 as a class, but especially to the Arthrostracous Orders' 2 ). In Ger- 

 many a similar opinion has been expressed by B ö r n e r 3 ) who 

 shows that the mandibles and their musculature are closely com- 

 parable in the Arthrostraca, the Apterygota, and the nymphs of 

 Ephemerida while those of the winged insects are quite distinct. 

 He argues further, from a study of the abdominal gills in the 

 ephemerid larva that these structures are appendicular in nature, 

 claiming thus a near correspondence between primitive insects 

 and isopods. In America, Hansen's work has obtained 

 strong support from Folsom's studies on the maxillulae of 

 Collembola, both in the adult insect 4 ) and in the embryo 5 ), so 

 that the appendicular nature of these structures can no longer 

 be doubted. 



*) Zoolog. Anzeiger XVI. 1893. 



2 ) Art. „Arthrofioda" in E n c y c 1. B r i t. ed. X. (Quart. Journ. Micr. 



Sei. XLVII. 1904.) 



3 ) Zool. Anzeiger XXXIII. XXXIV. 1909. 



4 ) Bull. Mus. Comp. Anat. Harvard XXXV. 1899. 



5 ) Ib. XXXVI. 1900. 



