Mermis Parasitic on Ants of the Genus Lasius. 363 



a moment and then shot out to a short distance, but still remained 

 attached to the worm by a colourless gelatinous sul)stanco. When 

 a sufficiently large group of eggs had in this mauuer collected 

 round the orifice, it broke away by its own weight. "When laid 

 inside the larval skin, in which there appears to be no vulvar 

 aperture, the eggs assumed the form of a flat ribbon as wide as 



a, Largest oocyte of normal female of Lasius alienus. 



b, Largest oocj'te of worker of Lasius alienus. 



c, Largest oocyte of parasitized female of Tjasius alienus. 



All to same scale. 



ov, ovum ; ovd, oviduct ; nc, nurse cells. 



the diameter of the skin, each egg being separated from its fellows 

 by the gelatinous material. Almost all the cast skins were full 

 of eggs, the egg-laying going on before, during and after the casting 

 of the skin. It is possible that the skin forms a useful protection 

 to the eggs, but the uterus after the casting of the skin contained 



2 c 2 



