252 Robert Wilhclm ITegner. 



sio ctwas iiacli dem Riicken binaiif unci liegen rechts und links vom 

 Riickengefass." 



Three species of beetles, Ilydropliilus piceus, Melolontha vulgaris 

 and Lina tremulw received brief mention by Graber 0891). In 

 Hydrophilus the two germ-glands were found lying near each other 

 on the dorsal w^all of the intestine, close to the proctodeum. In 

 Melolontha "Die Gonaden erscheinen bier sehr frlihzeitig als mit 

 dem Visceralblatt verbundene gestielte Korper, an denen man wieder 

 ein Zellepithel und mchrere grossere und kleinere Inhaltszellen 

 unterscheiden kann." In Lina the reproductive organs were dis- 

 covered anterior to the proctodeum in connection with the "Darm- 

 faserblatt." They appeared very similar to the corresponding organs 

 described by Wheeler (1889) in Leptinotarsa. 



In a Russian paper, ISTusbaum (1891) has figured at the posterior 

 pole of the egg of the oil beetle, Meloe proscarahcvns, a wedge-shaped 

 structure designated as an "accumulatio plasmatis et nucleorum in 

 posteriore polo ovi." This nucleated mass occupied the position of, 

 and is very similar in appearance to, the group of pole-cells and 

 pseudoblastodermic nuclei shown in Fig. 25 ; in this species there 

 probably occurred an early development of the germ-cells, such as 

 has been found in Chrysomelid beetles. 



The embryological development of the following species of Chryso- 

 melidce was studied by Lecaillon (1898) ; Clytra Iceviuscula, Gasiro- 

 physa raphani, Clwysomela menthastri, Lina popidi, L. fremiilce 

 Agelastica alni. In Clytra, the principal form examined, Lecaillon 

 found the first nuclei which arrived at the posterior pole of the egg 

 to become the primitive germ-cells ; these could be distinguished 

 from neighboring cells by their large size, larger nuclei, and darker 

 cytoplasm. The germ-cell nuclei did not stop when they reached 

 the surface of the egg, but passed outside and became separated 

 from it; their number increased "pen a pen par suite de I'arrivee 

 de nouvelles cellules peripheriques et aussi sans doute de la division 

 des premieres cellules detachees du pole de I'oeuf." The germ-cell? 

 then started to re-enter the egg, retarding, by this migration, the 

 formation of the blastoderm at this point. 'Tinalement, le blasto- 

 derme achcve de se former au pole posterieur de Tauf, et alors 



