I04 
ZOOLOGY OF THE FAR EAST. 
Hydrozoa that inhabit brackish water in the Oriental Region ; and to compare them 
with those forms that have established themselves in fresh water. By "inhabit" I 
mean, live out their full life-cycle. Medusae and hydroids attached to floating objects 
that are carried into the mouths of marine lakes or into the creeks of deltaic tracts 
by the tide and are able to survive for short periods in water of low salinity have 
not, in the present state of our knowledge, the same interest. 
At present we know of only five hydroids and three hydromedusae that inhabit 
brackish water connected with the Indian Ocean.' They are : — 
It will be as well to consider each of these species separately. 
Evidence for the association of the medusa Asenathia with the polyp Annulella 
is still far from complete. The latter was originally introduced into an aquarium in 
Calcutta among weeds from small ponds of brackish water in which also it was sub- 
sequently found. These ponds are situated at Port Canning on the Mutlah (or Matla) , 
a tidal river that formerly connected the vSalt Lakes on the outskirts of Calcutta with 
the head of the Bay of Bengal, but now that the lakes have been to a large extent 
drained, forms merely part of the network of waterways covering the lower region of 
the Gangetic delta. The water both of the ponds and of the river is of low but ex- 
tremely variable salinity, which is constantly changing in the latter with tide and 
season, and in the former owing to evaporation and rainfall. The organisms in the 
ponds have been introduced in floods from the river. Whether Asenathia and An- 
nulella, therefore, are to be regarded as two species or as two generations of one 
species, they come from practically the same locality and live in similar circumstances. 
Neither has been found elsewhere. 
In the case of Dicydocoryne , another genus originally obtained from a pool of 
brackish water at Port Canning, the adult medusa is not known, but the young 
medusa has been described from specimens budded off in captivity. The species 
{the hydroid only) has also been found in the Chilka Lake, but the genus is as yet 
monotypic and apparently endemic in waters connected with the Bay of Bengal. It 
has not been found in the open sea. 
Bimeria fluminalis is a species of a small but widely distributed marine genus 
perhaps not to be distinguished from the much larger genus Perigonimus , which is 
also marine. So far as we know, B. fluminalis, which has not been found in the open 
1 The only other Coelenterates that we know to inhabit brackish water in Eastern Asia are the Schizostomous 
medusa Acromitus rabanchatii, the Actiniaria Edivardsia tinclrix, Halianthus limnicola, Metridium schillerianum, Phvtoccetes 
gangeticus. Ph. chilkaeus, Pelocoetes exul and Gvrostoma ^lamitin, and an unidentified Alcyonarian of the genus 
V irgularia. 
Hydroids. 
Medusae. 
Annulella gemmata, Ritchie 
Dicydocoryne filamentata (x\nnand.) 
Bimeria fluminalis^ Annand. 
Campanulavia serrulata (Bale) 
Campanulina ceylonensis (Annand.) 
7 
Asenathia piscatoris, nov. 
D. filamentata (Annand). 
no medusa, 
no medusa. 
Phortis ceylonensis (Browne). 
