Germ-Cells in Chrysomelid Beetles. 281 



appeared from view beneath tlie egg. One cell lying near the anterior 

 end of the egg was capable of amoeboid movements, bnt its identity 

 was not established. Ritter (1890), after finding that the pole- 

 cells in Clilronomus penetrate the blastoderm, concludes that "anders 

 als durch aktive Bewegnng konnen sie wohl kaum in die Lage 

 kommen, in welcher wir sie Fig. 10 finden." The cells in the figure 

 mentioned have, however, a spherical form exhibiting no pseudopodia- 

 like processes. 



Turning now to the Coleoptera, we find sufiicient evidence , to 

 prove that the pole-cells migrate by means of amoeboid movements. 

 Although Wheeler (1889) failed to find the pole-cells in the very 

 early stages of Leptinotarsa, he figures several of them (his Fig. 82) 

 in a sagittal section of an egg carrying a segmented germ-band. 

 Here are shown three cells "which are on the surface of the embryo 

 in the amniotic cavity. They are very large and clear and the more 

 anterior is apparently creeping in the manner of an Amoeba, along 

 the surface of the abdominal ectoderm. These cells, the ultimate fate 

 of which I have been unable to determine, probably escape from the 

 anal orifice of the gastrula before it closes." This author also shows 

 in transverse section (his Fig. 87) a cell which, he says, is "about 

 to wander through the blastopore into the amniotic cavity." He 

 suggests that this may be the homologue of the "Polzellen." My 

 sections prove that these are really pole-cells and that they creep 

 along the surface of the ectoderm by amoeboid movements, but the 

 direction of their migration is the reverse of that stated by Wheeler, 

 i. e., they are not wandering outward into the amniotic cavity but 

 are on their way into the embryo. 



In Clytra and other species of Chrysomelid beetles, Lecaillon 

 (1898) finds that the "cellules sexuelles," as he designates the pole- 

 cells, migrate back into the egg shortly after their appearance. In 

 another species (Gastrophysa rapliani) studied by this author, these 

 cells remain outside of the egg until a later stage oi development, 

 and then they penetrate the "ectoderm." Lecaillon does not present 

 any evidence to account for this migration, he says, however, that 

 these cells "se montrent en general moins bien fixees que les autres 

 cellules." In my material no difiiculty was experienced in obtaining 



