'24 MUS MINüTUS. 



but had always looked upon them as a mere conglomera- 

 tioa of dry grass. The greatest difficulty to observe these 

 little animals lies iu the particular mode of their distribu- 

 tion over the country. In general, they occur in isolated 

 couples in brushwood , cornfields and meadows , but nobody 

 will be aware of their presence, unless he detects one of 

 their nests ; and if he has the rare luck to find one , he 

 will soon conclude , that the species is spread over the coun- 

 try in single couples living at great distances from one 

 another. It is indeed an exceptional case , when they are 

 found forming a colony, and such a one is sometimes 

 restricted to a locality of little extent. When surprised 

 by inundation of the meadows, they are sometimes seen 

 flocking together in considerable numbers, trying to save 

 themselves by climbing up to the crown of grass and plants. 



The system of colonisation of this animal is , however , 

 not permanent, the colony being often reduced in the 

 following year to a small number of couples. No doubt , 

 that the increased number produced by a favourable mul- 

 tiplication in certain years , contributes to the fluctuation 

 observed in the distribution of these animals. 



I now purpose to enter into some details about a co- 

 lony of the Dwarf-Mouse I met with in the summer of 

 the year 1868, in a locality, not examined before that 

 time in its whole extent , and of which colony only a small 

 number of couples remained in the following years. This 

 locality is situated at the distance of about two miles from 

 the town of Leiden, in the neighbourhood of the castle 

 of Endegeest, celebrated for having served as a refuge to 

 the philosopher Descartes, after his exile from France. 

 There exists , on the right side of the road , leading to 

 the neighbouring village of Rynsburg, not less celebrated 

 for its Abbey and as the residence of the freethinker 

 Spinoza, a ditch of about a quarter of a mile in 

 length and six paces in width , intersecting a field 

 planted with vegetables. Its right border was for one 

 half of the length, grown with high reed, the other 



PJ'ote» from the Leyden INXuaeum, "Vol. III. 



