before they develop. The production of these two
kinds of eggs is a device to overcome the cold of winter, or the drying
up of the pools in which the species lives, during the heat of the
summer. The power of resistance which such eggs possess may be seen in
the fact that a sample of mud which had been kept dry for ten years
still contained living eggs. In deep water where neither drought nor
winter cold can seriously affect the _Daphnias_, they propagate all the
year round by unfertilized "summer" eggs.

BIBLIOGRAPHY.--For further details on this subject the following
authors should be consulted:--_Mammals_: F. E. Beddard, "Remarks on
the Ovary of Echidna," _Proc. Roy. Phys. Soc. Edin._ vol. viii.
(1885); W. H. Caldwell, "The Embryology of Monotremata and
Marsupialia," _Phil. Trans. Roy. Soc._ vol. 178 (1887); E. B. Poulton,
"The Structures connected with the Ovarian Ovum of the Marsupialia and
Monotremata," _Quart. Journ. Micros. Sci._ vol. xxiv. (1884). _Birds,
Systematic_:--H. Seebohm, _Coloured Figures of the Eggs of British
Birds_ (1896); A. Newton, _Ootheca Wooleyana_ (1907); E. Oates, _Cat.
Birds' Eggs Brit. Mus._ (appearing), vols. i.-iv. published.
_General_:--A. Newton, _Dictionary of Birds_ (1896). _Colouring
matter_:--Newbegin, _Colour in Nature_ (1898). _Reptiles and
Amphibia_:--H. Gadow, "Reptiles," _Camb. Nat. Hist._ (1901); G. A.
Boulenger, "The Tailless Batrachians of Europe," _Ray Soc._ (1896).
_Fishes_:--Bridge and Boulenger, "Fishes, Ascidians, &c.," _Camb. Nat.
Hist._ (1904); B. Dean, _Fishes Living and Fossil_ (1895); J. T.
Cunningham, _Marketable Marine Fishes_ (1896). _Invertebrate_:--G. H.
Carpenter, _Insects. Their Structure and Life_ (1899); L. C. Miall, _A
History of Aquatic Insects_ (1895); T. R. R. Stebbing, _Crustacea_,
Internat. Sci. series (1893); M. C. Cooke, "Mollusca," _Camb. Nat.
Hist._ (1906). For further references to the above and other
Invertebrate groups see various text-books on Entomology, Zoology.
(W. P. P.)

EGGENBERG, HANS ULRICH VON, PRINCE (1568-1634), Austrian statesman, was
a son of Siegfried von Eggenberg (d. 1594), and began life as a soldier
in the Spanish service, becoming about 1596 a trusted servant of the
archduke of Styria, afterwards the emperor Ferdinand II. Having become a
Roman Catholic, he was soon the chancellor and chief adviser of
Ferdinand, whose election as emperor he helped to secure in 1619.