DEVELOPMENT OF BEES 
267 
Fig. 2.—-Three stages to the development of the egg (greatly magnified). The earliest stage at which 
the rudiments of the appendages are seen is represented by a and b; a, egg seen from the ventral (lower) 
side; b, from the right side; c, later stage, showing the development of the mouth parts, silk glands, etc.; 
d, embryo just prior to hatching, the development within the egg being completed; An, anus; Ant, antenna; 
Br, brain; 1L, 2L, 3L, thoracic legs; Lb, labium (lower lip) ; Lm, labrum (upper lip) ; Md, mandible; MT, 
malpighian tubules; 1 Mx, 2Mx, first and second maxillae; SlkGl, silk gland; Sp, rudiment of spiracle; Tr, 
trachea; VNC, ventral nerve cord. 
tissue cells is shown in Fig. 1. A cell may 
be defined as “a mass of protoplasm (liv¬ 
ing material) containing a nucleus.” Both 
nucleus and protoplasm are interdepend¬ 
ent; neither is capable of continued exist¬ 
ence without the other. The nucleus (N) 
is a body usually more or less rounded in 
form, containing within it a substance com¬ 
monly believed to be the bearer of the 
hereditary qualities of the individual and 
of the race. Every cell is to a certain ex¬ 
tent independent, carrying on its own vital 
functions, such as the assimilation of nour¬ 
ishment and the elimination of waste. In 
addition, in the higher organisms, it usual¬ 
ly has a special function; for example, 
the special function of the liver cell is to 
secrete bile, that of the nerve cell to trans¬ 
mit nerve impulses. All the cells in an 
organism are, however, so co-ordinated 
that the sum total of their activities is a 
unified whole, that is, an individual, capa¬ 
ble, under the proper conditions, of main¬ 
taining itself and contributing to the re¬ 
production of its kind. One property of 
the protoplasm and nucleus of a typical 
cell is the power of multiplying by self¬ 
division. This division always produces 
daughter cells, each receiving a part of 
the parent cell. In Fig. 1 two cells are 
in process of division. 
On beginning its development every egg 
is essentially a single cell. In addition to 
the protoplasm and nucleus of a typical 
cell, the egg contains also a certain amount 
of non-living material, yolk, which serves 
as a store of food for the developing em¬ 
bryo. Before it can begin development, the 
unfertilized egg or female cell must usually 
be first united with a much smaller and 
more condensed cell, the spermatozoon, or 
male cell. This cell supplies the male half 
of the inherited characters and also stimu¬ 
lates the egg into development. This phe¬ 
nomenon is fertilization. In certain cases 
eggs may develop without the stimulus of 
the spermatozoon, and they therefore in¬ 
herit their characters only thru the mother; 
this is parthenogenesis. 
The development of the egg or cell 
formed by the union of the male and fe¬ 
male cells consists in its repeated division, 
by which many cells, united together, are 
formed; the shifting and rearrangement of 
these to form organs and tissues; the grad¬ 
ual appearance of differences between the 
cells forming the various tissues and or¬ 
gans, so that the cells become changed or 
