268 Sex Inheritance in Pediculus hiimanus var. corporis 



tunately certain errors have occurred in that article, and it is very difficult 

 to trace the histories of the various families. The present account con- 

 tains a more complete record of the experiments, and also corrections of 

 the former paper. 



The cytological examination of fertilization in Pediculus has been 

 undertaken by Dr Doncaster, who is continuing the study of the sex 

 problem presented by this parasite. 



Material. 



In all cases the lice used were collected from verminous clothing 

 sent from London by Dr Hamer. The clothes-lice for any particular 

 series of experiments came off the same piece of cloth, and presumably 

 from the same host. In all cases they belong to the race Pediculus 

 humanus var. corporis, and there was no evidence of the presence of 

 var. capitis, although the possibility of the occurrence of hybrids between 

 these two races should not be ignored, especially in view of the results 

 obtained by Bacot (1917), and Keilin and Nuttall (1919) on hybridisa- 

 tion in lice. 



On the arrival of a batch of lice, the larvae were removed from the 

 adults and placed on a piece of black cloth in a glass tube. This was 

 kept in an incubator at a temperature of about 30° C. and the lice were 

 fed twice daily, morning and evening, on the arm\ 



As soon as an adult emerged it was removed to a separate tube, in 

 order to avoid the possibility of any unknown crosses with other emerging 

 adults, and in all cases where a female was found in the same tube as 

 a male, it was not used for any breeding experiments. 



A selected male and female were then placed together in the same 

 glass tube and provided with a small piece of black cloth, on which to 

 hold and to lay eggs, and, except in the case of a few experiments, were 

 kept in the same tube and fed together until they died. 



When the lice were placed on the arm they usually began to feed 

 at once and gorged themselves in a few minutes. The female com- 

 menced to lay eggs about 24 hours after emerging from the larval 

 skin, and generally continued to lay 2 to 4 eggs daily for about four 

 weeks. It should be emphasised, however, that the number of eggs laid 

 by a female fed only twice daily is considerably less than the number 



I. ' 

 1 This method has now been improved upon by Nuttall (1917) who obtains much 

 better success with his " pill-box method," whereby the parasites may be kept continually 

 on the body. 



