Some years ago it was propagated in an extraordinary manner on roebucks in the woods of the Duke of Arenburg, in the environs of Louvain. They are sometimes found also on man. We know of two instances: the first is that of a lady at Antwerp, who had a small tumour on her shoulder, which was removed, and enclosed a living tick. Leeuwenhoek gives an instance of a woman of the lower classes who had a tick in the middle of her stomach. Moquin-Tandon relates that Raspail found some on the head of a little girl four or five years old. He also gives an instance of a young man who, returning from hunting, found a tick under his arm; and while on the site of a 143 sheep market, a servant found one morning three attached to the skin of his breast. Delegorgue speaks of some very small reddish ticks in Africa, which cover the clothes by thousands, and produce distressing itching. Others are found in different parts of the globe, and twenty-four species have been described. Several new American Ixodes have been noticed lately by Mr. Packard on the stag, the monax marmot, the _Lepus palustris_, &c. These arachnida live at first in freedom in the bushes, but after fecundation the female attacks the first mammal which she finds in her way, and establishes herself upon it; dogs become infested with it by running in and out among the brushwood. The _Argas reflexus_ lives on pigeons, and is allied to the _Ixodes_. R. Buchholz has lately studied many new acaridæ found on different birds.