. Text-book de l'embryologie. L'embryologie. VIII 251 AETHEOPODA » macrosegments", qui par la suite sont réparties dans les segments définitif ; mais comme le soi-disant " macrosegments " ne correspond pas à l'autre en valeur dans différents insectes, il ne semble pas qu'ils ont des caractères morphologiques d'importance, ou que l'apparence de la divisant hnes hors de l'ordre approprié est d'une importance plus que la fin de la démarcation de la chélicère segment dans la procephalic au lobe arachnides. Dans la région de l'embryon Bonacia est d'abord divisé en un proto- région céphalique et un so

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. Text-book of embryology. Embryology. VIII AETHEOPODA 251 " macrosegments, " which subsequently are subdivided into the definitive segments; but as the so-called " macrosegments " do not correspond to one another in value in different insects, it does not appear that they have any morphological importance, or that the appearance of the dividing hnes out of their proper order is of any more importance than the late demarcation of the chelicera segment from the procephalic lobe in Arachnida. In Bonacia the embryonic area is first divided into a proto- cephalic region and a so-called " protocormic " region, which includes all the rest of the body by a single transverse line of division. The. Fig. 199.—Three surface views of the embryo of Donacia crassipes when the germinal streak begins to show division into segments. (After Hirschler.) A, ventral view of early stage. B, ventral view of later stage. G, lateral view of about the same stage as that represented in B. a&, vestigial abdominal appendage; ant, rudiment of antenna ; hyp, rudiments of hypopharynx ; il-3, rudiments of the three walking legs ; lab, rudiment of labrum ; mn, rudiment of mandible; maji, rudiment of first maxilla; -mifi, rudiment of second maxilla; o, mouth ; stig, rudiments of stigmatae; stig (at the posterior end of C), the last enlarged stigma. protocormic region is then divided by two transverse lines into a "jaw " region, a " thoracic " region, and an " abdominal" region. In each of these regions the definitive segments are first marked off at their respective hinder borders. Thus we find a stage with two segments in the jaw region, the hinder of which is the second maxillary segment; and with two in the thoracic region also, the hinder of which is the segment of the metathorax, which later bears the third leg. This is succeeded by a stage in which the three definitive jaw segments and the three thoracic segments are clearly marke

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