MOSQUITOES AND FIL ARIAS IS 143 



of the muscles. They are then about eighteen to twenty 

 micromillimetres in diameter, and a little slenderer than 

 those Avhich remain in the muscles. By the twentieth 

 day those remaining- in the thorax have grown larger and 

 have begun to break down the muscular tissue. Those 

 which have migrated are found to have penetrated the 

 neck, accumulating in the head, and penetrating into the 

 beak. The question of transmission then becomes very 

 much like that of the transmission of the malarial germs, 

 and it seems reasonably sure that the Filaria is inocu- 

 lated directly into the skin by the beak of the mosquito, 

 and it is in the skin of man that the parasite accomplishes 

 its last metamorphosis and becomes adult. In the skin 

 they pair, and the embryos, issuing in the lymphatic 

 spaces or vessels, are carried by the lymph into the blood- 

 Thus the life round is comjDlete. 



The mosquito which is concerned in this work is not an 

 Anopheles, as is the case with malaria, but a Culex. The 

 one studied by Bancroft in Australia is one of the com- 

 mon domestic Australian mosquitoes, Culex ciliaris 

 Linn., which is possibly a synonym of Culex pipiens Linn. 

 Other species may be involved, and, in fact, other biting 

 insects than mosquitoes, but these points are not yet 

 thoroughly determined. 



