42 Records of the Indian Museum. [Von. V, 
Indian specimens, as well as several of the varieties, would suggest 
that the type is preserved with considerable exactness, and this 
view is confirmed by the fact that several distinct forms are fre- 
quently found growing together in conditions so absolutely identical 
that their zoaria are intertwined.! 
Two better tests as to the distinctness of ‘‘ forms ’’ could not, 
in my opinion, be found ; but whether these *‘ forms ’’ should all 
be recognized as ‘‘ species’’ is another question. Personally I 
think that it would be inconvenient to adopt a course so extreme. 
I have been forced, therefore, to devise a test for distinguishing 
“species ’” frome. vatieties..”” Dhe-test: adopted: is-as -artincial 
as all such tests must be in the present unsettled state of biological 
knowledge. I have called those forms (7.e., groups of specimens) 
““species,’’ the differences between which are so constant and so 
clear that it is possible to express the more important of them in the 
form of a key to the genus; while my “‘ varieties’’ are groups 
of specimens separated from those comprised in the nearest species 
by differences that do not appear to be altogether constant or are 
of a kind that cannot be represented easily in words or numbers. 
The question of ‘‘ subspecies’’ (7.e., local races) hardly arises 
as regards Plumatella, for there is little evidence that such races 
exist in the genus. 
Up to the present time I have been unable, owing to unfavour- 
able climatic conditions, to carry out direct biological experiments 
as to the effect of environment on the individual zoarium in the 
Polyzoa, but evidence obtained in the unnatural environment of 
an aquarium is usually unsatisfactory as regards such points, and 
I think that the facts stated above will at any rate make my 
position clear as regards the ‘“‘ species’’ and ‘‘ varieties ’’ des- 
cribed below. 
Key to the Indian species of Plumatella. 
Group I. (Repens group.) 
Ectocyst more or less rigid, pigment- 
ed or colourless; tip of the zoce- 
cia rounded when the polypide is 
retracted. 
1. All the zocecia entirely recum- 
bent, having the aperture on 
the dorsal surface and a strong 
furrowed keel; ectocyst col- 
ourless and transparent ; free 
statoblast elongate =. . Pi javanica: 
2. The younger zocecia as a rule 
forming long free branches, 
each with the aperture at the 
tips a furrowed keelymever 
a’ 
| In a pond in the Calcutta Zoological Gardens I have found the following 
forms growing together in this way :—P. /fruticosa (with the phase corallotdes), P. 
emarginata (with the phase benedeni), the varieties diffusa and dumortieri of 
P. allmani, P. javanica and P. punctata. 
