THE EMBRYOLOGY OF THE HONEY BEE 55 



cordingly the external surface of the germ band must also dis- 

 play evidences of segmentation in the form of a faintly wavy 

 contour" (p. 530). 



It is not clear whether the difference just mentioned between 

 the superficial aspect of the iritersegmental and intrasegmental 

 cells of the germ band applies to the ventral or lateral plates. 

 Both were examined in the most favorable preparations, but no 

 differences could be noted. In longitudinal sections of the ven- 

 tral plate, however, such as that represented by figure 22A, a 

 considerable difference between the form of intersegmental and 

 intrasegmental cells is noticeable, the latter being much nar- 

 rower at their outer ends than the former. 



Both Kowalevski (1871) and Heider (1889) described a 

 precocious segmentation in the egg of Hydrophilus, the latter 

 investigator finding it expressed in the form of transverse folds 

 which appear even before the middle plate is found. Both 

 Kowalveski and Heider interpreted these as corresponding with 

 the future definitive segments. Carriere (1890) found that 

 the egg of the mason bee (Chalicodoma) also showed a precocious 

 segmentation essentially the same as that just described for the 

 honey bee. At the "flask" stage, or even earlier, segmentation 

 makes its appearance on the ventral plate, in surface views of 

 the egg, as dark transverse bands, alternating with lighter ones, 

 accompanied by a corresponding lobing of the lateral folds. The 

 anterior segments appear first, afterward those lying caudad, in 

 rapid succession. According to Burger's statement (1897) seg- 

 mentation appears first in the lateral plates, and only later in the 

 middle plate. The individual segments become very sharply 

 marked out, much more so than in the honey bee. Since the 

 first rudiments of the embryo (antennae, mouth parts, etc.) 

 appear very early in Chalicodoma as early as the "flask" stage, 

 and therefore long before the completion of the union of the 

 lateral folds, the early identification of the individual segments 

 is made possible. In both Chalicodoma and Apis it is important 

 to note that the segments appearing thus precociously are the 

 definitive segments of the insect (the so-called microsomites) 

 and that there is no previous separation of the germ band into 

 the larger divisions seen first by Ayers (1884) in Oecanthus, 

 afterwards by Graber (1888) in the representatives of several 



