ANCYLOSTOMA DUODENALE 



453 



surface by the larva, but it is simply the old skin, which is not cast off, 

 but is retained for purposes of protection, as the larva is free living, 

 but casts it as soon as it assumes parasitic life again. From the egg 

 to this mature stage is thus six to ten days. 



FIG. 331. Ancylostoma duodenale: left, four days after transmission into 

 dog, 190/1 ; in the centre, at the commencement of the second stage of develop- 

 ment (five to six days), 105/1 ; on the right, fourteen to fifteen days after trans- 

 mission. 42/1. (After Looss.) 



Bionomics of Development. Air : Eggs can develop when shut 

 off from the air for a " comparatively long " time. 



Temperature : Hatching takes from eight hours upwards. Eggs 

 develop best at 25 to 30 C., but will not develop below 8 to 10 C. 

 The larvae, however, will stand freezing. 



