Genn-CV'lls in Chrysomclid Beetles. 255 



8. Dermaptera. 

 The primitive germ-cells were identified by Heymons (1895) in 

 Forficula auricidaria soon after the blastoderm was completed, form- 

 ing- a group at the posterior pole of the egg. At this time they could 

 not be distinguished from the blastoderm-cells, but soon their nuclei 

 became larger and clearer. The germ-cells increased rapidly by divi- 

 sion and formed a spherical Ixidy, the genital rudiment. ''Paracytcn" 

 wore abundant near the germ-cells, and ''Audi einzelne Genital- 

 zellen pflegen iiicht selten zu degeneriren, und zwar unter denselben 

 Erscheinungen, die wir an den Paracyten kennen gelemt haben." 

 The genital rudiment was pushed anteriorly near the dorsal surface 

 of the body, l)y the lengthening of the germ-band, AVlien the primi- 

 tive seg-ments a})peared, the germ-cells, which lay in the tenth to the 

 eleventh segments, were, by the bending of the posterior end of the 

 body, forced into the ninth segment. They now separated from one 

 another and migrated anteriorly by means of amoeboid movements 

 until they reached the sixth and seventh abdominal segments. Some- 

 times a few germ-cells were left behind in segments eight, nine, ten, 

 or eleven. Now the germ-cells separated, half going to either side 

 of the embryo, and moved anteriorly into the third to the seventh 

 abdominal segments. ]\[ost of the germ-cells of the male remained 

 in seg-ments five, six and seven ; those of the female were distributed 

 approximately uniformly through segments three to seven. 



9. Altera. 



Heymons (1897) has given a clear account of the primitive germ- 

 cells in a Thysanuran, Lepisma saccliarina. In this insect a knob- 

 like projection was observed at the hinder end of the germ-band; 

 this projection was composed of cells with large nuclei containing less 

 chromatin than the nuclei of the mesoderm-cells, which had also 

 begun to appear. These larger nuclei were interpreted as germ- 

 cells and arose from the ectoderm. The primitive germ-cells migrated 

 just as they were found to do in Orthoptora (Heymons, 1895), 

 "Stets gelangen die Geschlechtszellen an die dorsalen Ursegment- 

 wandungen, dringen in dieselben ein und bilden zusammeu mit den 



