146 DR. CHARLES CHILTON ON THE SUBTERRANEAN 
it the third uropoda are not elongate and their outer branch 
consists of one joint only. 
The affinities of Miphargus were fully discussed by Wrzesni- 
owski in 1890, and in the present state of our knowledge it does 
not appear possible to add very much to what he then said. Its 
nearest allies seem to be the Neoniphargus already mentioned 
and Crangonyx, with the genera Paracrangonyx and Hucrangonyx 
lately established by Stebbing, while the little-known marine genus 
Eriopsis also seems to be nearly related. Naturally enough it 
has frequently been compared with Gammarus, since freshwater 
species of this genus are often present in the districts where the 
subterranean Wiphargi are found. Wrzesniowski has pointed out 
that most of the external characters of Miphargus are shared by 
various species of Gammarus, and that consequently these alone 
are not sufficient to distinguish the two genera; he has, how- 
ever, shown that there are important differences in the mouth- 
parts, and these he has described in great detail. Although 
there are considerable differences between the mouth-parts of a 
typical Gammarus and a typical Miphargus, there are already 
known some intermediate species, and no doubt others will here- 
after be described which will still further bridge over the gap 
between the two. Some of the numerous species from Lake 
Baikal referred to Gammarus by Dybowsky present external 
resemblances to Wiphargus; but although many of them have 
been assigned to new genera by Stebbing, no satisfactory account 
of their mouth-parts has as yet been published, and without this 
it would be useless to attempt any detailed comparison. In his 
account of the genus Crangonyw Professor Vejdovsky has drawn 
special attention to the sensory sete found on various parts of the 
body aud appendages; and he tells me that in these and also in 
some parts of the internal anatomy, especially in connection with 
the renal gland in the base of the lower antenne, he has found 
good points of difference not only between allied genera such as 
Gammarus, Niphargus, and Crangonyx, but in some cases even 
between different species of the same genus—a paper dealing with 
these points willshortly be published by him. It is unfortunate 
that most of these characters, important as they are, can be 
observed only in fresh specimens or require to be elucidated 
by the cutting of serial sections, and that consequently they 
have been and, toa large extent, probably will continue to be 
neglected by the systematist. 
