NATUHAL HISTOKT OF THE GENUS DERO. 



103 



D. latissima, aa also in a pond between Sutton and Hedhill on 

 the high road, and later D. limosa. The latter is especially 

 abundant in the Lily-tank at Kew. D. obtusa and D. JPerrieri 

 are to be found in the large pond on Wandsworth Common; and 

 both sjDecies, as well as D. 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, B. limosa, D. oUusa (Belgium only), and the doubtful 

 D. digitata. Of these, the first two are widely distributed, 

 ranging from the United States to South E-ussia 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 Oligochseta 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 Naidomoupha, Vejdovsky. 

 Genus Dero, Oken. 

 Proto. — Xantlio, JDutrocliet. — Nais digitata, Milller. 

 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 obhged 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. 



