134 ANIMAL PARASITES AND MKSSMATES. 



remarkable instance of this in the Acarus marginatus of 

 Hermann. On the 18th Thermidor, an 2, they were 

 making a post mortem examination at Strasburg of a man 

 who had died of fracture of the skull, and when opening 

 the dura mater, they saw on the corpus callosum, a mite 

 running about which became the type of the species. 

 The appearance of this acarus under such conditions 

 made, as may be supposed, much noise at the time, but 

 we should not be surprised if it had been introduced 

 during the operation by a fly seeking to lay its eggs. 



In this group is found another interesting acarus, 

 which is developed in man in the sebaceous crypts of the 

 nostrils. The name of Simonea has been given to it, 

 from Dr. Simon of Berlin, who made it his especial study. 

 This genus leads us by its form to the Linguatulae, the 

 structure of which has been so long doubtful. The 

 Simonea folliculorum belongs to the family of the Demo- 

 dicidse. 



The dog harbours a demodex (D. Caninus) which causes 

 it to lose its hair. Some years ago, the sheep in Bel- 

 gium were attacked by one of the acaridae, the Ixodes 

 reduvius, which had been introduced from a neighbour- 

 ing country, and had multiplied with frightful rapidity. 

 Packard has given an account of an Ixodes bovis on the 

 Erethizon epixanihus, and on the Lepus Bairdii, and an 

 Argas Americana on cattle coming from Texas ; this 

 was published in the sixth report of the United States' 

 Geological survey (1873). 



According to the observations of Mons. Megnin, the 

 Tyroglyphi, the Hypopi, the Homopi, and the Trichodactyli, 

 are transitory forms which ought not to be preserved 

 as generic divisions among the acaridae. We have found 



