510 



7^. W. Hegner 



at the end away from the axis of rotation and a breaking out is 

 frequent in this region. 



Ill THE ORIENTATION OF THE EGGS OF CALLIGRAPHA BIGSBYANA 



It has been known for more than twenty years that the eggs of 

 insects are definitely oriented within the ovaries of the adults. 

 Hallez in 1886, finding this to be true of the ova of Hydrophilus and 

 Locusta, expressed the fact in his " Loi de I'orientation de I'embryon 

 chez les Insectes" as follows. "La cellule-oeuf possede la meme 

 orientation que I'organisme maternel qui I'a produit: elle a un 

 pole cephalique et un pole caudal, un cote droit et un cote gauche, 



Fig. I A diagrammatic drawing of C. bigsbyana clinging to the under side of a willow leaf and showing 

 the orientation of the egg in the ovarian tubule and after deposition. 



Fig. 2 Four eggs of C. bigsbyana laid in two rows. a. = anterior, d. = dorsal. /. = left. p. = 

 posterior, r. = right, x. = anterior ventral surface where the spot of India ink was placed as a guide 

 for orienting the eggs during the experiments. 



une face dorsale et une face ventrale; et ces differentes faces de la 

 cellule-oeuf coincident aux faces correspondantes de I'embryon." 

 No difficulty is experienced in distinguishing the anterior from 

 the posterior end of the eggs of Chrysomelid beetles as it is always 

 the posterior end which first emerges from the vagina. This end 

 is fastened to the leaf on which the egg is laid and subsequently 

 becomes the posterior end of the embryo, regardless of the posi- 

 tion of the leaf. In only two species (Calligrapha multipunctata 

 and C. bigsbyana) of the many Chrysomelid beetles examined 

 could the right and left sides of the egg be accurately determined. 

 The egg laying of these insects is as follows: "The beetle selects 



