110 
ZOOLOGY OF THE FAR EAST. 
and bra( kish- water Coeleiiterates structural modifications can be discovered, and in 
some cases these modifications can be definitely correlated with unfavourable cir- 
cumstances, such as silt in suspension or deposited or the danger of a sudden change 
in conditions of life ; but in none can we yet say that this or that character is 
an adaptation for life in water of low or variable salinity. So far as this element 
in the changed conditions is concerned, the physiological evolution involved in the 
change of habitat has been much more comprehensive than the anatomical. The 
only features of a general kind that all the genera and species have in common 
are negative — a small size and lack of brilliant or conspicuous pigments ; even con- 
vergence is not indicated. 
SYSTEMATIC DESCRIPTION OF THE COLLECTION. 
HYDROZOA 
Order GY MNOBLASTEA. 
Family CLAVIDAE. 
Genus Cordylophora, Allman. 
This genus, which for long was regarded as monotypic and as essentially fluviatile 
and lacustrine, is now known to include several marine species. 
Cordylophora lacustris, Allman. 
1868. Crodylophora lacustris, Hincks, Brit. Hydr. Zooph., p. 16, pi. liii, fig. 2. 
1871. Cordylophora lacustris, Allman, Mon. Gymn. Hyrd., p. 252, pi. iii. 
.^1887. Cordylophora ivhiteleggei , v. Lendenfeld, Zool. fahrb. II, p. 97, pl.vi, figs. ii-i2. 
I find among my collections from the Tai-Hu (Great Lake) in the Kiangsu Pro- 
vince of China several Hydroid colonies that agree in every respect, so far as the 
hydrophyton is concerned, with examples of Cordylophora lacustris from England, 
Germany and Egypt. Unfortunately none of them bear gonosomes. The largest 
colonies are about 3 cm. long. They were attached with the polyzoon Paludicella 
elongata - to mussel-shells [Modiola lacustris, v. Martens), which in their turn were 
fixed to the roots of willow-trees. The Tai-Hu is an inland freshwater lake connected 
by numerous creeks with the Yangtse system, but not by any main waterway; a 
sketch map is reproduced on p. 4 of this volume. 
So far as I am aware, C. lacustris has not previously been recorded from the Far 
East. It occurs in fresh and brackish water in many parts of Europe, N. America 
and western Asia , and has been found in the almost land-locked Sea of Azov ' and the 
now isolated salt-lake Birket-el-Qurun,* which was formerly connected with the Nile. 
The Australian form C. whiteleggei, v. Lendenfeld is perhaps no more than a dwarfed 
1 Motz-Kossowska, Arch. Zool. experim. (4) III, pp. 63-67 (1905). 
2 Annandale, Mem. As. Soc. Bengal VI, p. 30 (1916). 
» Ostrooumoff, Bull. Ac. Imp. Set. St. Petersbourg (5) IV, p. 400 (1896). 
+ C. L,. Boulenger, Quart. Journ. Micr. Sci. LII, p. 358 (1908). 
