474 ROBERT W. HEGNER 



Buchner's ('10b) contention that the 'besonderer Korper' of 

 Sagitta is the remains of the 'accessory fertiUzation cell' of Ste- 

 vens ('04) is not sustained by either Stevens ('10) or Elpatiewsky 

 ('10). The nucleolar nature of the 'Aussenkornchen' in Cyclops 

 ('97) was later discarded ('03) and the conclusion was reached 

 "dass ich die Aussenkornchen ahnlich wie die Nukleolen, fiir 

 temporare, nicht-strukturierte Abscheidingen oder Zwischen- 

 produkte des Kern-Zelle-Stoffwechses halte, welche in ganz 

 bestimmten Zustanden der Zelle zur Abscheidung gelangen 

 bezw. wieder aufgelost werden" (p. 308-309). Amnia ('11) 

 has considered this subject at some length, and after rejecting 

 the possibilities of these being of (1) chromatic, (2) nucleolar, 

 (3) chromidial, or (4) mitochondrial origin, concludes that 

 they are transitory structures and "dass die Ectosomen als 

 Abscheidungen Endprodukte des Kern-Zelle-Stoffwechsels auf- 

 zufassen sind," (p. 557). In this way the Keimbahn-determinants 

 in copepods are satisfactorily explained, and a similar explanation 

 may be applied to Sagitta, although with less certainty. 



c. From a differentiated part of the cytoplasm. A review of 

 the literature on the Keimbahn-determinants and the investi- 

 gation of these substances in the eggs of insects force me to con- 

 clude that the fundamental organization of the egg is 'responsible 

 for the segregation of the primordial germ cells, whereas the 

 visible substances simply furnished evidence of this underlying 

 organization. As I have stated elsewhere (Hegner, '08, p. 21), 

 regarding the Keimbahn-determinants in beetles' eggs, "the 

 granules of the pole-disc are therefore either the germ cell determi- 

 nants or the visible sign of the germ cell determinants." The 

 writer's experiments have thus far failed to determine the exact 

 function of these granules. When the posterior end of a freshly 

 laid beetle's egg is pricked with a needle, not only the pole-disc 

 granules flow out, but also the cytoplasm in which they are im- 

 bedded (Hegner, '08). If a small region at the posterior end 

 be killed with a hot needle the pole-disc is prevented from tak- 

 ing part in the development of the egg, but so also is the sur- 

 rounding cytoplasm. Eggs thus treated continue to develop 

 and produce embryos without germ cells, but, as a rule, a part of 



