president’s address. 
135 
a single water-lily leaf, the originally distinct colonies of Pl. repens 
become so crowded together as to assume a somewhat Alcyonelloid 
appearance. Colonies of this type occur, with the typical Pl. repens, 
at Cringleford. Pl. fungosa owes its origin, according to the same 
author, to the germination of a number of the so-called “ sessile ” 
statoblasts on some cylindrical object. The juxtaposition of these 
statoblasts results in the crowded growth which is so characteristic 
of PL fungosa. AVesenberg-Lund has made the further observation 
that the old colonies, which may be as large as a child’s head, are 
the result of several years’ growth ; and that when cut vertically 
they show one or two dark annual rings, indicating that the colony 
is two or three years old, as the case may be. It is not certain 
whether the new growth which takes place in the spring is the 
result of the germination of statoblasts in the old tubes, or whether 
the old individuals remain alive through the winter and start 
a fresh growth in the spring. Further observations on this subject 
would be of interest. 
Turning to marine Polyzoa, I would direct your attention to the 
remarkable structures known as “ avicularia,” which are found in 
a large proportion of the Order Cheilostomata. These curious 
structures are regarded as modified individuals of the colony, in 
which the “ operculum ” which closes the orifice of the ordinary 
individuals has been modified into the “ mandible ” of the avicu- 
larium. They owe their name to the extraordinary resemblance 
possessed by the most specialised type of avicularium to a bird’s 
head. In the common genus Bugula, each is mounted on a short 
stalk, on which it executes various movements ; the jaws being 
used for the capture of organisms which stray over the surface of 
the colony. So much is well ascertained, but it is by no means 
easy to know whether the avicularia perform any function other 
than that of defence ; since they are totally devoid of digestive 
organs and, moreover, have no power of passing the substances 
they have caught to the mouths of the ordinary individuals. 
The subject is well worthy of further observation made on the 
living colony ; but I have ventured to suggest* that one of their 
# Quart. Journ. Micr. Sci. vol. xliii., 1900, p. 236. 
