48 Journal of the Asiatic Society of Bengal. [February, 1912. 
instances is afforded by the green cells that are found in the 
substance of many freshwater sponges. These cells have the 
structure of simple Algae and are believed to benefit the 
sponge in which they live by producing for it nutritive sub- 
stances and possibly also oxygen. They have been culti- 
vated artificially as independent organisms but in a state 
nature are only known in association with sponges 
selves close together it is found that they are invariably 
embedded in a common gelatinous substance which it was 
believed that they themselves secreted. Prof. W. West, how- 
selves, it is possible that the common investment of the 
polyzoon is produced by the efforts of a symbiotic Alga rather 
Another genus of polyzoa closely allied to Pectinatella is 
Lophopodella, the type species of which (L. carteri) occurs in 
India and also in East Africa and Japan. The colonies of this 
IT. 
“Every autumn, in a English pond or lake, a crisis takes 
place in the affairs of the less highly organized inhabitants, 
and preparations are made to withstand the unfavourable con- 
ditions due directly or indirectly to the low winter temperature 

'J.A.8.B. (N.S.), VIL, p. 83 (1911), 
