INSECTS, 271 
individuals occur, which being incapable of propagating have been 
commonly considered to be sexless (the so-called neuters, working- 
bees, &c.) Even the external form indicates that they resemble 
rather the female than the male individuals, as the same is also 
indicated by their mode of life and their instinct directed to the care 
of the young ones. Anatomical investigation has confirmed this 
conclusion by demonstrating in the working-bees imperfect ovaries?. 
These individuals thus remain imperfect females, nurses, foster- 
mothers. 
Observations are not wanting with respect to the development 
of Insects in the egg, although iiknig this subject has not been 
sufficiently investigated to allow a general representation of it to be 
offered. In eggs ‘that are just laid, nay in those which he at the 
lowest part of the oviduct and are the most mature, the germinal 
vesicle has disappeared ; in eggs situated higher up in the oviduct 
it may be seen clearly with the germinal spot?. On the yelk is 
formed, from a union of cells, a layer as germinal membrane (b/asto- 
derma) which continues to grow so as to surround the entire yelk. 
The first rudiment of the embryo, the nota primitiva, lies on the 
ventral surface; the yelk lies on the dorsal surface, and becomes 
enclosed by the constantly growing ventral plates, without the for- 
mation of a special umbilical- or yelk-sac by constriction. The 
stigmata are developed only at a late adi and become open only 
shortly before the escape from the egg’. 
1 MaApDEM. JURINE in Huser Nouv. observations sur les Abeilles, 2e édit. Paris et 
Genéve, 8vo. 11. Tab. XI. fig. 1, figure copied by RaTzEBURG in his enquiries on this 
subject in Nov. Act. Acad. Ces. Leop. Car. Vol. Xvi. Pl. 1. Tab. 47. 
2 See the microscopic representation of an egg-tube from Agrion, by R. WAGNER, 
Abhand. der mathem. physic. Klasse der Akademie in Miinchen, Bd. u. fig. 1 ; see 
s. 558. 
> On the development of insects in the egg there are some observations of Suckow, 
Anatomisch-physiologische Untersuchungen der Insecten und Krustenthiere, Heidelberg, 
1818, 4to. mit Kupf. s. 19, 23, 35 (eggs of Bombyx pint); also short, but interesting 
communications by RaTHKE, on Blatta germanica in MECKEL’S Archiv. 1844, s. 27— 
37, Taf. 11. (here there is on each side of the abdomen in the embryo, behind the attach- 
ment of the third pair of feet, a pediculated disciform organ which is, perhaps, a tem- 
porary respiratory organ to be compared with the gills of larvee of salamanders ; there 
are only four Malpighian vessels, which are increased in number after birth), and 
finally, by KOELLIKER (on Chironomus, Simulia, Donacia) Observationes de prima 
Insectorum genesi Diss. inaug. Adjecte sunt 111. Tabul. Turici, 1842, 4to. The numerous 
plates of Huroxp in his Lisquisitiones de Animalium vertebris curentium in ovo 
