454 Dr. A. Dohrn on Eugereon Boeckingi. 



incomplete metamorphosis will not hold their ground against 

 a sharper examination and criticism of the facts. 



Hackel has also entirely given up this principle of division, 

 and retained instead of it the form of the buccal organs, so 

 far as they are arranged either for biting or sucking. Whether 

 this is a permanent principle must be shown hereafter, when 

 more means of observation may be employed than at present. 

 Discoveries like Eugereon, in a palseontological direction, and 

 the larva of 8isyra (described by Westwood as Branchiotoma 

 8i)ongillce, see Gerstacker and Carus, ' Zoologie,' p. 73), which, 

 as I have been informed by Professor Grube, and also find 

 repeated in Gerstacker's ' Handbuch,' likewise has a sucking 

 buccal apparatus, although its imago belongs to the Neuro- 

 ptera, are certainly adapted to render the certainty of this mode 

 of division somewhat doubtful. However, it is of no con- 

 sequence whether or not there is such a principle of division ; 

 when we have a knowledge of the ontogenetic and phylo- 

 genetic development we can subsequently select any principle 

 we like, and employ it for the sake of convenience. For the 

 present we must adhere to Hackel's classification. Hackel is 

 of opinion that the first Protracheate (belonging to the hypo- 

 thetically adopted family produced from the Zoepoda, but 

 which still united in itself the germs of the Insecta, Arach- 

 nida, and Myriopoda), which possessed two developed pairs of 

 wings, is to be regarded as the common progenitor of all the 

 living and fossil insects known to us, as the apterous forms 

 undoubtedly all (?) originate from winged ancestors, and have 

 lost their wings by adaptation and secondary generation. The 

 development of this progenitor falls in the interval between 

 the Siliu'ian and Carboniferous periods, and probably in the 

 ante-Devonian period ; for we have insects from the Devonian 

 as well as from the coal, and these are exclusively Masticantia 

 (Orthoptera, Neuroptera, Coleoptera). These Hackel regards 

 as the oldest insects, in opposition to the Sugentia, which have 

 branched off from the Masticantia ; and this is certainly pro- 

 bable when we glance at the ontogenesis of the former. The 

 Masticantia he divides into three orders: — Toroptera^ Coleo- 

 pteray and Hymenoptera. The Toroptera are the scarcest, 

 and combine the Pseudo-Neuroptera, Neuroptera, and Ortlio- 

 ptera, which are very nearly allied to each other in many re- 

 spects, and were formerly only separated by the metamor- 

 phosis. As, however, the systematic value of the metamor- 

 phosis, as a means of division, has been diminished, these 

 former orders are certainly justly united. Hackel thinks that 

 the Orthoptera and Neuroptera have been developed from the 

 Pseudo-Neuroptera — an opinion which obtains a foundation of 



