NATURAL HTSTORY OP THE GENUS DERO. 
95 
of observing it for himself, did little more than copy Muller’s 
description. Johnston (14) merely mentions the genus to 
throw doubt on its right to a position in the British fauna 
at all. 
In 1S55, for the first time since Muller noticed the genus 
under consideration, we meet with an attempt to give something 
like an exact account of a new species. In that year a paper 
appeared from the pen of D’Udekem (6), which must be regarded 
as the starting-point of all modern work on the subject. Up to 
that time Dero digitata aud D. f areata, (the latter of which had 
almost been lost sight of) had held the field alone ; but D’Udekem’s 
contribution contained a description of a new species, Dero 
obtusa , clearly expressed, and accompanied by a figure which 
rendered it easily recognizable. 
In 1872 Perrier (22) published a very interesting and exhaustive 
account of a species which he identified with that described by 
D’Udekem ; and the fact that he w r as w r rong on this point in no 
way detracts from the value of his observations, whilst his figures 
are almost all that could be desired. In acknowledgment of 
Perrier’s work, I have named the species which he studied Dero 
Derrieri , it being new. 
Prof. Leidy (15), in a paper of which he has kindly sent me 
a reprint, describes two worms, one of which he calls Dero limosa 
and the other Aulophorus vagus. The former appears to be 
identical with a species found abundantly round London ; the 
latter is considered by Prof. Leidy to be identical with that 
described by Bosel {Joe. cit.), the Dero furcata of Oken ; and 
apparently Prof. Leidy ’s distinction is based upon the fact that 
he found the latter free. 
Semper (26) has described two species under new names, his 
Dero philippinensis being apparently the same as Dero limosa just 
referred to, whilst Dero Bodriguezii is undoubtedly the same as 
the Aulophorus vagus of Leidy, Dero furcata of Oken, and Dero 
palpigera of Glrebincky. 
Tauber’s work (29) contributes nothing to our knowledge of 
the genus, being merely a catalogue of Danish Annulata. He 
remarked that the genus is rare in Denmark. 
The magnificent work of the Bohemian Professor Vejdovskv 
(31) contains a full list of names and synonyms of the species of 
Dero known up to the date of bis publication. Unfortunately 
he observed only a very few examples of the genus, the species 
8 * 
