64 
the parasites now known to be Copepods were not at 
first recognised as Crustacea, chiefly because of the diffi- 
culty of making out the true characters and the absence 
of knowledge as to the life-histories. There was much 
difference of opinion even as to which were really the 
anterior and posterior extremities of these animals, due 
to the fact that the posteriorly placed ovisacs of the then 
known forms are cylindrical tubes which were by some 
supposed to be the antennules, and therefore that end 
was called the anterior. Hence many of the drawings of 
the earlier authors represent the animals standing on their 
heads. 
Baird’s “ British Entomostraca,” published by the 
Ray Society in 1850, marks an important epoch in our 
knowledge. This author gives an interesting historical 
account of the group, brings together all that was pre- 
viously known, and gives a very full account, with 
excellent figures, of all the British species known at 
that time, and although some of these are inaccurate in 
detail, or have been added to by more recent investiga- 
tions, still Baird’s monograph is indispensable to any one 
working at the subject. Since 1850 comparatively little 
has been done in this country to increase our knowledge 
regarding the distribution or habits of these crustaceans. 
Within the past few years, however, the study has revived 
and some important papers, mainly speciographic, have 
been published. 
The latest classification of the Copepod fish parasites 
arranges them under seven families, as follows :—Ereast- 
LIDH, CaLicipm, DicHeLEstipm, Parinicntayip®, LERNIDA, 
CHONDRACANTHIDEH, and Lernmopopipm. With the excep- 
tion of the Puimicurnuyipm, all these families have 
representatives living on fishes found in the seas around 
our coasts. 
