98 MR. G. 8. BRADY ON THE 
curious also that although the marine species advance into fresh 
water, we do not find the fresh water species tolerate even a 
very small admixture of salt; for except the Stickleback, I have 
never noticed any fresh water animal in the saline pools. 
Professor T. Rupert Jones in his “ Monograph of the Fossil 
Estherix,” says that some of the fresh water HEntomostraca 
“may have been capable of living, at least for considerabie 
periods, in even salt water, for some of the common Cyprides, 
such as are abundant in fresh water streams, are not uncommon 
in ditches of brackish and even highly saline water in the low 
grounds near the sea.” I must say that this is quite contrary 
to my experience, and at all events I do not think it can be a 
thing of common occurrence. I have never met with any of the 
fresh water Entomostraca in brackish pools, nor have I ever in 
such situations found any species of Cypris; the only Ostracoda 
which I have taken belonging either to the genus Cythere or 
to the sub-genus Cyprideis. The Corophium is found inhabiting 
tubular burrows on a soft muddy or peaty soil: it is always, so 
far as I have observed, associated with numbers of Annelids, and 
though it undoubtedly has the power of burrowing rapidly into 
the mud, I believe that the tubes in which it is found are really 
the work of the ‘Annelid. And if, as it is asserted, there be 
such a deadly enmity between the two creatures, it is not at all 
an impossible circumstance that the Corophium, after demolish- 
ing the unfortunate Annelid, may add insult to the injury by 
taking possession of its burrow. The constant presence of Coro- 
phium in localities of this kind where no communication with 
the sea is possible would seem to contradict the assertion of M. 
Quatrefages (quoted by Spence Bate and Westwood in their 
History of the British Sessile-eyed Crustacea) “ that at about 
the end of April they come from the open sea in myriads to 
wage war with the Annelids, which they entirely destroy before 
the end of May; they then attack the mollusca and fish all 
through the summer, and disappear in a single night about the 
ena of October, and return again the following year.” 
Estuarine swamps such as this which we have just noticed 
seem to be the nearest analogues we now possess of those exten- 
