52 Records of the Indian Museum. [VoE! ahs 
of the radial canals. Death is thus extremely gradual. All these 
points are clearly important in considering the systematic position 
of any medusa that exhibits the slightest signs of degeneracy. 
II.—LIFE HISTORY OF THE HYDROID AND MEDUSA. 
By R. E. LLoyp. 
In July 1915, Dr. Annandale informed me of the occurrence 
of the Medusa, Irene ceylonensts (Browne), in the brackish water of 
a canal in the neighbourhood of Calcutta and suggested that I 
should enquire into its life-history as his own observations on the 
subject had to be discontinued. He also kindly lent me a stained 
permanent preparation showing several planulae, some with bud- 
ding hydroids and stolons. This preparation was made by Mr. 
F. H. Gravely from material gathered from the bottom of a glass 
bowl in which a number cf the medusae with ripe gonads had been 
confined for observation, 
About the middle of July, the medusae were plentiful 
throughout the canal so that I was able to obtain a large number, 
varying in diameter from about 2°5 mm. to 2.5 cm. By the end 
of the month however none were to be found. No doubt they 
were killed by the heavy monsoon rain, which greatly diminishes 
the salinity of the water. 
I was unsuccessful in again raising the planulae in captivity 
but was fortunate in obtaining some colonies of the hydroid grow- 
ing in the canal attached to stones. Some were kept alive for ten 
days, affording good opportunity for observation. Several gene- 
somes were obtained from these colonies. These were stained and 
mounted in Canada balsam. They show certain stages in the 
development of the medusa, especially the early and late stages, 
in a satisfactory manner. 
The Hydroid Colony. 
The hydroid was defined by Dr. Annandale from material 
taken in brackish water at Port Canning, but as I had the oppor- 
tunity of examining the living animal from day to day in the 
laboratory a few further remarks on its structure will be made. 
The hydroid varies considerably in size Only the larger and 
older individuals can be discerned by the naked eye. The colony 
as a whole is much less conspicuous than most hydroid colonies. 
The stolon seldom divides, so that it is easy to strip off as much 
as an inch from the substratum without meeting any outgrowths 
except the hydrothecae. The stolon however does occasionally 
branch, the growing point dividing in a simple dichotomous 
manner. 
The coenosarc of the stolon has a different appearance from 
the coenosarc of the hydroid, due principally to the fact that the 
endoderm cells of the stolon are granular and opaque while those 
of the hydroid are clear, vacuolated and much larger. The hy- 
