THE EMBRYOLOGY OF THE HONEY BEE 45 



bands, which will later form the amnion together with the 

 strictly embryonic division, may be conveniently considered as 

 together constituting the ventral plate. Later, when the amnion 

 begins to be more clearly differentiated, the embryonic portion 

 of the ventral plate, which now constitutes the embryonic rudi- 

 ment, is commonly known as the germ band. 



This stage is introduced by the appearance, on the ventral 

 surface of the blastoderm, of two narrow longitudinal ridges, 

 sharply defined on their inner margins, less so on the outer. As 

 seen in surface view, they appear as shown in figure IV, where 

 they have the appearance of gently curved and slightly irregular 

 dark lines with their convex sides facing one another, like re- 

 versed parentheses, )(, and separated from each other at the 

 point of closest approximation by a distance of about one-eighth 

 of the total circumference of the egg at this point. The distance 

 between their anterior ends and the cephalic pole of the egg, is 

 about equivalent to the egg's diameter here ; their length when 

 first visible from the exterior is, as shown in the figure, about 

 one-fourth of the total length of the egg. As development pro- 

 ceeds these ridges extend rapidly caudad, diverging slightly at 

 first and then pursuing a course nearly parallel to one another 

 as far as the caudal pole of the egg, embracing between them a 

 strip of blastoderm whose average width is almost one-sixth of 

 the circumference of the egg at any given point (Fig. V). This 

 strip is the middle plate, and constitutes the future mesoderm, 

 while the embryonic blastoderm laterad of it on each side forms 

 the lateral plates, whose mesial edges are the lateral folds. 



Simultaneous with the caudad extension of the lateral folds 

 (Stages IV-V) is a movement of their anterior portions toward 

 the mid-line. This movement begins first at about that point 

 where the folds originally approached one another most closely, 

 that is, about one-fourth of the length of the egg from its cep- 

 halic pole. The anterior ends of the folds meanwhile remain 

 stationary. The outline of the folds in consequence of their 

 movement toward one another near their anterior ends, forms a 

 figure more or less resembling an elongated flask (Fig. V). In 

 the corresponding stages of Hydrophilus (Kowalevski, 1871), 

 and Chalicodoma (Carriere and Burger, 1897), the resemblance 

 between the outline of the folds and that of a flask also occurs 



