(49) A. Brandt. Ueber das Ei u. seine Bildungsstätte. Leipzig, 1878.
(50) T. H. Huxley. “On the agamic reproduction and morphology of Aphis.” Linnean Trans., Vol. XXII. 1858. Vide also Manual of Invertebrated Animals, 1877.
(51) R. Leuckart. “Ueber die Micropyle u. den feinern Bau d. Schalenhaut bei den Insecteneiern.” Müller’s Archiv, 1855.
(52) Fr. Leydig. Der Eierstock u. die Samentasche d. Insecten. Dresden, 1866.
(53) Lubbock. “The ova and pseudova of Insects.” Phil. Trans. 1859.
(54) Stein. Die weiblichen Geschlechtsorgane d. Käfer. Berlin, 1847.
[Conf. also Claus, Landois, Weismann, Ludwig (No. [4]).]
The ovum of Insects has formed the subject of numerous investigations, and has played an important part in the controversies on the nature of the ovum.
The ovaries are paired organs, rarely directly connected, each consisting of more or fewer ovarian tubes which open into a common oviduct. The oviducts unite into a vagina, usually provided with a spermatheca and accessory glands, which need not be further alluded to. Each ovary is invested by a peritoneal covering, which assumes various characters, and either forms a loose network covering the whole or a special tunic round each egg-tube. It is continuous with the general peritoneal investment. Each ovarian tube ([fig. 17]) consists of three sections: (1) a terminal thread, (2) the terminal chamber or germogen, (3) the egg-tube proper.
Fig. 17. A. Ovarian tube of the Flea, Pulex irritans. (From Gegenbaur, after Lubbock.)
o. ovum. g. germinal vesicle.
B. Ovarian tube of a Beetle, Carabus violaceus. (After Lubbock.)
o. ovarian segment, formed of an ovum a, and a mass of yolk cells, b.