STUDIES ON GERM CELLS 
IV. PROTOPLASMIC DIFFERENTIATION IN THE OOCYTES OF CERTAIN 
HYMENOPTERA 
ROBERT W. HEGNER 
From the Zoological Laboratory of the University of Michigan, 
Ann Arbor, Michigan, U. S. A. 
NINETY-EIGHT FIGURES (THIRTEEN PLATES) 
CONTENTS 
I. The differentiation of the oocytes and nurse cells in the ovaries of the 
RMN AEG. PAIS, MNGUINANO Fo cielo 's pickin « Wiae «vs ola,0 ate halote eeualia Samet neeaenels 495 
Il. The bacteria-like rods and secondary nuclei in the oocytes of Camponotus 
hercuieanus. var. penusylvanicaDeG.: ....0....5..0nccss Ren we eine 506 
Ill. The history of the nuclei and germ-line determinants in the oocytes of 
certain parasitic Hymenoptera and Hymenopterous gall-flies......... 521 
i OM pI ON OMIA, POlCENIAE S.Moore m/s cde’ Sic ke 8 Ln aie os + odie a ieee anaes ;.. 521 
Pee Nambeles SIOMCTALIEGNa a Aagte, Pope oo bee a os 3 5 6 vin a oe oan a atenenetane 526 
See Ep meno pPberOUs Ca MNIER. 4 och d.oly.< bie.c 6 = + vie. a ape dcaekte ore meme ene 529 
Literature cited 
I. THE DIFFERENTIATION OF THE OOCYTES AND NURSE CELLS IN 
THE OVARIES OF THE HONEY-BEE, APIS MELLIFICA 
As the writer has recently pointed out (Hegner ’14 ¢), there 
are in many animals two definite periods in the germ-cell cycle 
during which germ cells and somatic cells arise from the same 
mother cells. One period occurs during embryonic development 
when the primordial germ cells are segregated. This segre- 
gation takes place at different stages of development in different 
species. For example, in the midge, Chironomus, one of the 
first four cleavage cells gives rise to all of the germ eells (Hasper 
’11); in the paedogenetic fly, Miastor, the primordial germ cell 
is differentiated at the eight-cell stage (Kahle 08; Hegner ’14 a) 
but in most cases where a very early segregation has been ob- 
served, one cell at the thirty-two-cell stage is the primordial 
germ cell, as in Ascaris (Boveri ’92), in Cyclops (Haecker ’97; 
495 
JOURNAL OF MORPHOLOGY, VOL. 26, NO. 3 
