338 PHYLUM ARTHROPODA. 
of. the cockroach. The blood contains a few nucleated 
amceboid corpuscles. 
The excretory system consists of numerous fine Mal- 
pighian tubules which open into the small intestine. 
Reproductive system.—In the drone the reproductive 
organs consist of a pair of testes, each furnished with a 
narrow vas deferens, expanding at its distal end into a 
seminal vesicle. The seminal vesicles open into the ejacu- 
latory duct, and at their junction a large paired mucus gland 
opens. When maturity is reached, the testes diminish in 
size, while the spermatozoa accumulate in the terminal 
expanded part of the ejaculatory duct, and there become 
aggregated into a compact spermatophore. With the ter- 
minal portion of the male duct copulatory organs are 
associated. 
Mating takes place only once in the life of the queen, 
and is followed by the death of the drone. 
In the queen the large ovaries occupy considerable space in the 
abdominal region. As usual, each consists of numerous (100-150) 
ovarian tubes, containing ova in various stages of maturity. The 
ovarian tubes open into the right and left oviducts, which again unite 
to form the common oviduct. With the anterior portion of the common 
duct the globular spermatheca is associated. In connection with it 
there is a gland corresponding to the mucus gland of the male. The 
oviduct terminates in a copulatory pouch. 
Previous to laying, the eggs are fertilised by sperms set free from 
the spermatheca. In the case of drone eggs, this liberation of sper- 
matozoa does not take place, and the eggs in consequence are partheno- 
genetic. Queens which have never mated, or which have exhausted 
their stock of male elements, habitually lay drone eggs, but those which 
are laying abundant fertilised eggs at times also lay unfertilised eggs. 
This withholding of spermatozoa is said to be ‘‘ voluntary,” and 
related to the needs of the colony, but the physiological reason is 
unknown, 
The workers possess female organs similar in type to those of the 
queen, but of an extremely rudimentary nature. 
The eggs are laid singly in the cells of the comb, at the rate of 
about two per minute, for weeks together. They are of the usual 
insect type. According to the size of the cell in which it is deposited, 
and the food with which it is furnished, the fertilised ovum develops 
into a worker or into a queen. The development takes place within 
the cell, and includes a complete metamorphosis. 
