PARASITES THAT ABE FREE WHEN OLD. 179 



in length, very thin, and twisted round each other, 

 which had been collected in the morning, on the flower 

 borders of several gardens within the city. It was 

 thought that there had been a shower of worms in the 

 night. 



There was not one male worm among three hundred ; 

 all were full of eggs, and the young ones were already 

 wriggling about within them. 



Whence come they? said I, in my article. Have 

 they fallen from the sky completely formed ? It is 

 evident that they have not been developed on the ground 

 where they have been found ; it is not less evident that 

 they appeared suddenly on the borders. Did they come 

 from within the bodies of certain insects which they have 

 quitted, on account of the rain which had fallen ? These 

 worms, in fact, had completed their parasitical stage in 

 the bodies of their hosts, and the great drought which 

 had continued for many weeks prevented their resuming 

 their first course of existence. It was the sudden eman- 

 cipation of so many worms at once which had attracted 

 the attention of gardeners : earwigs, cockchafers, and 

 many other insects give them shelter during the time of 

 this strange gestation. 



It is known, by the observations of Siebold, that the 

 eggs of the Mermis, laid during the winter, produce in 

 the following spring' embryos which live in damp earth. 

 They immediately seek the larvae of insects, perforate 

 their skin, and develop themselves there without be- 

 coming encysted. After this, they again pass through 

 the skin of their host, return to the damp earth, where 

 they change their skin, are fecundated, and lay eggs. 

 The larvae of Mermis albicans especially resort to cater- 



