542 Records of the Indian Museum. VoL: Xi 
and of a mode of transverse fission associated with the basal-bulb, 
and the structural uniqueness of the tentacles and of the chitin- 
covered basal-bulb itself. 
The examples of this minute but interesting species occurred 
in a valuable and extensive collection of Hydroids received from 
the Trustees of the Indian Museum for identification. It was 
first observed and collected by Dr. Nelson Annandale, during 
his investigation of the brackish water fauna of India; and to the 
fortunate fact that some living examples were kept for a short 
period in an aquarium is due Dr. Annandale’s record of the free- 
swimming medusoid generation. 
PROVENANCE AND HABITAT. 
So far the species has been found in only one locality—Port 
Canning, Lower Bengal; and in that locality it seems to be 
confined to a shallow brackish pond. At any rate careful search 
of material from other places in the neighbourhood of Port Can- 
ning has failed to reveal any trace of its presence. In the brackish 
water it occurs growing upon a delicate branched weed, the 
surface of which also bears many clusters of Acinetaria. The 
specimens were collected in the months of December, 1909 by 
Dr. N. Annandale, and in March, rgiIo by Mr. F. H. Gravely and 
Dr. B. L. Chaudhuri, and the latter are registered in the Natural 
History collections of the Indian Museum under the number ZEV 
3702/7. 
DESCRIPTION OF THE HYDROID. 
HABIT. 
The individuals are solitary, growing as a rule far apart from, 
and independently of each other. In very rare cases two indivi- 
duals may appear to be attached at their bases; but this is due to 
imperfect separation of their basal masses, which are held together 
in acommon growth of mucus. There is no coenosarcal connec- 
tion between such individuals, nor has any semblance to colonial 
development been observed. 
Consideration of the structures of this curious hydroid leads 
me to believe that the attached stage is merely a temporary 
phase in the life-history. This stage is, however, repeated again 
and again, each two periods of attachment being separated by an 
interval during which the hydroid is free. Whether during the 
free periods it floats in the water of the brackish ponds, or creeps 
upon the bottom, I do not venture to guess; but the analogy of 
Hypolytus peregrinus suggests that the Indian species may yet be 
captured in a tow-net, floating at the surface. In such case its 
minuteness would render difficult its detection in a miscellaneous 
plankton collection. 
The following facts point to the alternation of free and fixed 
stages. A hydroid individual in its attached stage consists of a 
