134 
president’s address. 
distribution of the species ; but it has been shown experimentally 
by Braem* * * § that the germinating power of the statoblast may be 
improved by exposure to the action of frost. f There can be no 
doubt that the statoblasts are a special adaptation to the conditions 
of fresh-water life : — in the first place, because they are only found 
in the forms which inhabit fresh water ; and in the second place 
because very similar structures are found in totally different groups 
of fresh-water animals. The so-called winter-eggs of the Crustacean 
Daphnia and its Allies are enclosed in a bivalve shell, the so-called 
“ephippium,” which has a striking similarity to a statoblast; and 
an arrangement not unlike the annulus of a statoblast is even 
present in the egg of Anopheles, \ the Gnat which has obtained so 
wide a reputation as the means by which the Malaria-parasite is 
carried from one human “host” to another. 
The genus Plumatella includes several forms of very distinct 
habit. Those which are characterised by having their tubes 
parallel with one another and at right angles to the substratum on 
which they are growing were formerly placed in a distinct genus, 
Alcyonella. There is, however, no reasonable doubt that Alcyonella 
is merely a form of Plumatella; and Kraepelin§ goes so far as to 
regard Alcyonella fungosa as a particular state of growth of 
Plumatella repens. Wesenberg-Lund|| regards them as belonging 
to two distinct species, but he shows that the form of the colony is 
greatly influenced by the amount of room which it has at its 
disposal. If a number of statoblasts germinate close together on 
* “Unt. iib. d. Bryozoen d. siissen Wassers,” Leuckart & Chun’s 
‘ Bibliotheca Zoologica,’ Heft 6, 1890, p. 82. 
t See, however, Wesenberg-Lund (C.), “ Biologiske Studier over 
Ferskvandsbryozoer,” ‘Vid. Medd. naturh. Forening’ (Copenhagen), 1896, 
p. xxix. 
4 Nuttall (G. H. F.) & Shipley (A. E.), “Stud, in relation to Malaria.” 
II. ‘The Structure and Biology of Anopheles' Journ. Hygiene, vol. i, 
No. 1, 1901, p. 49. 
§ “Die Deutschen Siisswasser-Bryozoen,” Abhandl. Yer. Hamburg, vol. x., 
1887, p. 122, etc. 
|| T. cit. p. vii. 
