The Urinary Organs of the Amphipoda. 
By 
W. Baldwin Spencer, B.A., 
Scholar of Exeter College, Oxford. 
With Plate XIII. 
Within the group Arthropoda very various structures are 
met with subserving the function of excretory organs. 
The most primitive are undoubtedly nephridia as yet known 
only to exist in one member — Peripatus, whilst the most 
generally occurring are the Malpighian tubes whose presence is 
highly characteristic of and possibly confined to the Tracheata ; 
indeed, this is usually considered a not unimportant point of 
difference between the latter and the Crustacea. 
Notwithstanding this it is known that in certain Crustaceans 
there do exist small but well-defined appendages opening into 
the posterior part of the alimentary canal, though whether into 
the mid or hind gut is a disputed point. 
In English text-books, with, so far as I am aware, but one 
exception, their existence is either passed over in silence or 
merely mentioned, whilst nothing definite is stated with regard 
to their nature and function. 
The one exception is the work of Messrs. Bate and West- 
wood on 1 Sessile-eyed Crustacea.’ Here their presence is 
fully recognised and a somewhat detailed description is given, 
though the power of cutting continuous sections enables us 
now to study their structure and relations more accurately 
than it was then found possible to do. 
VOL. XXV. NEW SER. 
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