390 INSECT A. 



eggs laid by the sexupara here give rise to the wingless sexual generation devoid 

 of proboscis and intestinal canal, which lays the winter-eggs. In Phylloxera 

 vastalrix, the young animals that develop out of the winter-eggs laid beneath 

 the bark of the trunk wander to the root, there to give origin partheno- 

 genetically to several generations of wingless Phylloxera, which cause the 

 swellings on the root. The series of these generations closes by the production 

 of winged sexupara, which wander up the trunk and swarm. These forms also 

 are parthenogenetic. Their eggs, which vary in size according to the sex of 

 the developing embryo, yield sexual animals devoid of proboscis, intestine, 

 and wings, which produce the winter -eggs. Parallel series are introduced 

 into this cycle of generations also, e.g., the wingless Tctrancura, living on 

 leaves which run parallel with the generations of Phizobia. In the cycle of 

 generations of the genus Chermes recently investigated by Blochmann (Nos. 

 134 and 135), Dueyfuss (No. 137), and Cholodkovsky, similar conditions 

 are found, but these are in some respects still very obscure. In Chermes abietis, 

 the fertilised egg gives rise to a wingless parthenogenetic female (fundatrix, I.), 

 which hibernates at the base of the buds of the fir-tree and, by piercing the 

 buds, deforms them into galls. From this generation is produced a second 

 (II.) consisting of winged parthenogenetic forms, some of which migrate to- 

 the larch and there give rise to a wingless generation (III.) which feeds on the 

 needles and hibernates beneath the bark. These parthenogenetic alienicolae, 

 in the following spring (the second year of the cycle), produce the winged 

 remigrantes (IV.) or sexupara, which return to the fir-tree and there produce 

 the wingless female and male, the fertilised eggs of which give rise once more 

 to a fundatrix (I.). This cycle also is accompanied by a parallel series of forms 

 that do not emigrate to the larch, but remain on the fir-tree. 



IV. General Considerations. 



It can hardly be doubted that the Insects and the Myriopoda are 

 very intimately related. If it is considered that the anatomical 

 features possessed in common and the similarity in development 

 (although, indeed, the ontogeny of the Myriopoda is only partly 

 known) are not sufficient to establish this relationship, great stress 

 can be laid on the presence of transition-types, such as the Symphyla 

 (Scolopendrel/a, Fig. 192) and Thysanura (Campodea, Fig. 193), 

 which connect the two groups. It has only to be pointed out here 

 that in the Thysanura, which are most intimately connected with 

 the Orthoptera, we have, in the absence of wings and in the presence 

 of the sac-like protrusible ventral sac, a recurrence of morphological 

 characters which, while they are wanting in the higher Insects, 

 are nevertheless found in the Myriopoda. On the other hand, the 

 Myriopoda are closely related to Peripatas, so that we are justified 

 in regarding the Onychophora, the Myriopoda, and the Insecta as 

 belonging to a single phyletic ontogenetic series, which, through 

 Peripatus, is linked on to the hypothetical racial form of the 



