ORGANS OF REPRODUCTION 239 



the genital opening, and is finally deposited. One female lays 

 several capsules, and breeding goes on throughout the year. 

 The number of eggs in a capsule varies ; in Blatta orientalis it is 

 about 16 ; in Blatella germanica about 40 ; and in Periplaneta 

 americana about 20. Parthenogenesis occasionally occurs. When 

 the eggs hatch the capsule splits and the young emerge. The time 

 taken to reach sexual maturity varies with the species, and 

 depends much on external factors such as food and temperature ; 

 an average time from e.^^ to imago in the common cockroach is 

 a year or a little less. This species has seven moults, but in no 

 cockroach is there a true metamorphosis (p. 247). 



