114 Memoirs of the Indian Museum. [Vol,. V, 1915.J 



The maximum vegetative growth of the hydrophyton, which in favourable con- 

 ditions must be rapid, takes place in the lake in the salt-water season, but gono- 

 phores are produced in the greatest numbers at the time when the lake is inundated 

 with fresh water. Indeed, the most favourable conditions for their production seem 

 to be those most unfavourable for the survival of the hydranths. In the northern 

 part of the main area in September, when the water was quite fresh, we found both 

 male and female colonies covered with gonophores on stems of drift-weed that had 

 been carried by the wind into corners among rocks and had begun to decay. Most 

 of the hydranths had perished, but most of the gonads were developing normally, 

 though a few were degenerate, especially in the male colonies — a circumstance that 

 occurs even in conditions that seem to be more normal. In active colonies growing 

 in water of moderate salinity gonophores were never found in profusion so great, but 

 many are present on the type-specimens, which were taken in water of a specific gra- 

 vity of 1 006. In these they are almost entirely confined to those parts in which the 

 organism is congested by its own luxuriant growth. They are accompanied by few 

 hydranths, though the younger and freer parts of the colonies were evidently in full 

 nutritive vigour and well supplied with active polyps. It is thus clear that in 

 Bimeria fluminalis, as in many other species, sexual reproduction is stimulated by 

 changes in environment that ultimately prove fatal to the colony. 



