270 Robert Wilhelm Ilegner. 



to the posterior end of the egg (Stage IST). The germ-cells, still 

 situated in the last two labdoniinal segments (Fig. 42), have crowded 

 close together ; they do not form, as in younger stages, a loose strand 

 on either side of the body, but now constitute a distinct organ, the 

 germ-gland. 



After the contraction of the embryo is completed, the tail-fold 

 no longer exists as such ; what was formerly the end of it is now 

 coincident with the end of the egg (Stage O). The posterior abdom- 

 inal portion of this embryo is shown in sagittal section in Fig. 43. 

 The gerai-gland lies between the splanchnic and somatic layers of 

 the mesoderm: its cells have moved closer together forming a more 

 compact organ than before. A frontal section clearly shows its posi- 

 tion relative to the other parts of the body (Fig. 54). 



Figs. 51, 52 and 53 are from transverse sections of embryos 

 seventy-five hours, eighty-six hours and one hundred five hours old 

 respectively; these illustrate three stages in the path of the germ- 

 glands as they are carried from the ventral to the dorsal side of the 

 body by the lateral growth of the embryo around the yolk. A sagittal 

 section of an eighty-six hour old embryo (Fig. 44) when compared 

 with that of an earlier stage (Fig. 43) also demonstrates the same 

 phenomena. 



Tn the oldest stage figured (one hundred five hours, Fig. 45) it 

 is possible to distinguish the sexes; the male gland is recognized 

 by a constriction which, appearing in its middle region, gives to 

 it a dumb-bell shape ; the female organ is distinguished both in 

 transverse (Fig. 53) and in sagittal (Fig. 46) sections by the 

 presence of the developing terminal filaments (tf.). 



IV. General Considerations, 

 1. The Granules of the Pole-Disc. 



So far as I have been able to learn, no author has described in 

 the eggs of Coleoptera a structure in any way corresponding to the 

 pole-disc. Wheeler (1889) failed to note its presence in Lepti- 

 notarsa; Lecaillon (1898) makes no mention of it in the chrysomelid 

 beetles he studied (see historical part), although in several species 



