594 
J. BRONTE GATENBY. 
2 b in PI. 32, fig. 24 (IP). 
2c in PI. 32, fig. 28 (IP.). 
3 in PI. 33, fig. 31 (IP.). 
4 in PL 33, fig. 32 (IP). 
5 in PI. 33, fig. 34 (IP). 
6 in PL 33, fig. 35 (IP). 
7 in PL 33, fig. 36 (IP). 
8 in PL 34, fig. 45 (IP). 
9 in PL 34, fig. 46 (LP). 
Discussion. 
(a) Nebenkern. — Sex determiner, spindle former, de- 
generation product, cliromidium, are only a few of tlie 
different characters supposed to be fulfilled by this curious 
aggregation of stick-like structures, known as the Neben- 
kern. 
In the first place we will examine the evidence that the 
Nebenkern determines the sex of a differentiating cell. 
Demoll, tracing the Nebenkern from about the time of the 
“Bukett stadium ” in the prophases of the heterotype divisions, 
thought that the subsequent development of this body was the 
lever which turned the cell to oogonium. It is quite true 
that it is at or immediately after the bouquet stage that the 
first definite evidence for the female sex 1 can be found, but 
had Demoll succeeded in following out the mitochondria he 
would have seen that the latter may show a differentiation 
towards one sex before the Nebenkern becomes in any way 
characteristic. DemolPs reservation that the “ sex chromo- 
some 33 probably influences the Nebenkern to act in a way 
productive of one sex or the other is interesting, but supported 
by no evidence. 
Briefly stated, I should think the following disposed of the 
u Nebenkern and sex 33 hypothesis 1 : 
1 Sex, female or male, I have used somewhat loosely instead of 
metamorphosis of indifferent cell into oogonium or spermatogonium ’> 
respectively. 
