32 
wulst’ (Rırter, 90) or the ‘ Keimbahnplasma’ (Hasper, ’11) in Calli- 
phora as the ‘ Dotterplatte’ (Noack, ’01), and in Miastor as the ‘ po- 
lares Plasma’ (Kane, ’08); Hesxer, 12, 14). In the Coleoptera, 
they have been found only in certain chrysomelid species, in the 
eggs of which they constitute the ‘ pole-disc’ (HEsNER, ’08, ’09a, ’09b, 
"41a, ’11b, °14; Wireman, ’10). Finally, Smvesrrr (06, *08) has de- 
scribed keimbahn-determinants in parasitic Hymenoptera. Peculiar 
bodies are known in the eggs of a number of other animals belonging 
to several different phyla but they have not yet been identified as 
keimbahn-determinants. 
Before presenting my original observations it will be necessary 
to give an account of the discoveries of SıLvsstkr (’06, 08). 
Sitvestri has described the embryonic development of both mon- 
embryonic and polyembryonic hymenopterous parasites. Of the former, 
Encyrtus aphidivorus and Oophthora semblides were studied; in both 
species the series of events were found to be similar. The egg at the 
time of deposition is elongated and irregularly oval in shape; it con- 
tains a germinal vesicle in the anterior region and a deeply staining 
body near the posterior end which is called by Strvestri the ‘ nucleolo ' 
and is stated to be derived from the nucleolus of the odcyte nucleus. 
The eggs may develop parthenogenetically or after fertilization; the 
unfertilized eggs produce males whereas the fertilized eggs develop 
into females. In either case two polar bodies are produced; these 
disintegrate later. The cleavage nucleus produces by a series of 
divisions a number of nuclei which migrate to the periphery as is 
the rule in insect development. The ‘nucleolo’ remains during this 
cleavage period unchanged near the posterior end; then, when cell 
walls appear, it becomes distributed among several of the cells thus 
formed. These multiply less rapidly than the other embryonic cells 
and are the only cells that give rise to the germ cells in the adult. 
It is thus obvious that there is here an early segregation of germ 
cells and that these germ cells differ from the somatic cells in the 
possession of part of the disintegrated ‘ nucleolo.’ 
The polyembryonic species described by SıLvesıkı are Copidosoma 
(Litomastix) truncatellus and Ageniaspis (Encyrtus) fuscicollis. The eggs 
of these species, when laid, are vase shaped, the posterior end corresponding 
to the base of the vase. Here also a germinal vesicle and ‘nucleolo’ 
are present, the latter almost always near the posterior end. Partheno- 
genetic eggs were found to produce males whereas fertilized eggs give 
