338 PHYLUM ARTHROPODA. 



of the cockroach. The blood contains a few nucleated 

 amoeboid 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. 



