NATURAL HISTORY OF TITE GENUS BERO. 
103 
J). latissima, as also in a pond between Sutton and Redhill on 
tlie bigli road, and later D. limosa. The latter is especially 
abundant in the Lily-tank at Kew. D. obtusa and D. Perrieri 
are to be found in the large pond on Wandsworth Common; and 
both species, as well as JD. latissima and the rare _D. acuta , have 
been found in the pond at Greenwich Park. The last-named 
species was also found for the first time by my wife in the 
Crystal-Palace basin. 
Abroad the only species known to have been found are D. 
furcata, D. limosa , D. obtusa (Belgium only), and the doubtful 
P. digitata. Of these, the first two are widely distributed, 
ranging from the United States to South Russia and the Phi- 
lippine Islands. It will be seen, therefore, that at present the 
British Isles are apparently by far the richest in species of any 
known locality. Others doubtless remain to be discovered ; 
and to this end I am anxious to obtain samples of mud in a 
moist state from various localities abroad*; and South America 
especially should prove fertile in this direction. Much remains 
to be done before our knowledge of the minute Oligochgeta can 
be considered even fairly complete ; and it is quite possible that 
systematic observations in tropical and subtropical regions would 
reveal forms still more interesting and remarkable than those 
included in the genus Dero. 
My thanks are due to Mr. T. Bolton, whose kindness in sup- 
plying me with specimens has resulted in the discovery of one 
new species which has not yet been found elsewhere. 
The following is a systematic account of the various species at 
present known. 
Family Raibomorpha, Vejdovslcg, 
Genus Dero, Olcen. 
Proto.— Xantho, Dutrocliet. — Nais digitata, Muller. 
Char. Minute Annelids of from 40 to 100 segments, red- 
blooded, eye-less, inhabiting tubes secreted from the body, without 
aggregation of foreign material. The last segment bears an expan- 
sion from which arise four processes. Perivisceral fluid free from 
* I shall be much obliged for samples from any freshwater lake, pond, or 
tank, or even slow stream abroad. The best time for collecting would probably 
be before the rainy season in such localities as have one ; in those which have 
not, probably the end of summer would be best. The samples may be sent to 
me, care of the Linnean Society. 
