Germ-Cells in Clirysomelid Beetles. 273 



Granular inclusions have also been found in the eggs of other 

 insects, but show only a remote resemblance to the pole-disc granules 

 of Calligraplia. Thus Blockmann (1887) discovered a number of 

 bacteria-like rods in the undeveloped eggs of Blatta germanica. These 

 rods multiplied by division and were considered true symbiotic bac- 

 teria. The same author later described similar ''Stabchen" in several 

 siDecies of Hymenoptera (Camponotus Ugniperdus and Formica 

 fiisca. The eggs of Periplaneta orientalis and Ectohia livlda also 

 contain accumulations of ''bacterienartige Stabchen" which later 

 sink into the yolk and disappear (Heymons, 1895). 



At the present time, the nature of the pole-disc granules is un- 

 known; one of the two authors quoted above (Ritter, 1890, in 

 Chironomus) claims that the pole-disc ("Keimwulst") consists of 

 protoplasm, while the other (ISToack, 1901, in Calliphora) considers 

 it ("Dotterplatte") to be formed of yolk elements. I hold that the 

 disc is probably derived from the nucleus during the growth of 

 the oogonia. 



The origin of these granules may be difficult to determine, although 

 it seems not an impossible undertaking. Lack of material has pre- 

 vented me from tracing them in stages earlier than eggs of Leptino- 

 tarsa just previous to laying, at which time the polar bodies are being 

 formed (Fig. 2) ; here, however, the pole-disc is as large as in later 

 stages of development and it could doubtless be found in younger 

 eggs. 



A number of facts discovered in other invertebrates may be men- 

 tioned in favor of the nuclear origin of the granules of the pole- 

 disc. Blochmann (1886), Stnhlman (1886) and others have de- 

 scribed for various species of Hymenoptera a budding of the nucleus 

 in the oocytes;, these buds result in the formation of many small 

 "nuclei" ("Nebenkerne," Blochmann; "Dotterconcretionen," Stuhl- 

 mann) each containing small dark-staining granules. The "nuclei" 

 thus derived from the nucleus of the oocytes pass out to the periphery 

 of the cell and are lost to view. No pole-disc has been recorded 

 in any of these species of Hymenoptera, but in the Dipteron, Musca 

 vomUoria, where a pole-disc probably does occur, Korschelt (1886) 

 has described bodies in the oocytes similar to the "ISTebenkerne" of 



