194 L. A. BORRADAILE. 
Two or three more characteristics of varieties remain to be alluded to. In the first 
place it must be noted that varieties, like species, may be sundered by more than one 
difference, and that these differences, while they are, no doubt, smaller than those between 
most kindred species, can be easily paralleled by the latter in many cases, both m kind 
and in magnitude. Again, though the range of variation within a single variety is generally 
somewhat greater than that found in most homogeneous species, the latter will sometimes 
almost, if not quite, equal varieties in that respect. The differences between varieties are 
often less marked in the young than in old specimens, but this is the case with all the peculiar 
features of individual organisms. Lastly, there is, in many cases, no ascertained connection 
between varieties and locality, either geographical or bathymetrical, and they are not known 
to have any peculiar habits. 
As an example of a varietal’ species we may take Thalamita admeta (Hbst.), of whose 
varieties a key is given below in the second section of this report (p. 202). Here there 
are six varieties, resembling one another closely (that is, having the same range of variation) 
in most characters, but capable of separation by means of others, such as the depth of the 
frontal cleft, the fulness and granulation of the hand (propodite of the first leg), the size 
of the fourth side-tooth of the cephalothoracie shield; and so forth. These characters, be 
it noticed, are just such as are used in other cases to separate species of swimming crabs. 
Again, any two of the varieties may differ in one point only, or in more than one; and 
the varietal differences are less marked in the young than in old specimens. 
With the exception of two new varieties, which appear for the first time in the 
Maldive collection, but will probably be found ere long in some other part of the range 
of the J. admeta, the geographical distribution of these varieties is practically identical. 
There would be little doubt of findmg all of them in a sufficiently large collection from 
any part of the Indopacific region. Their bathymetrical distribution, on the other hand, 
would, if we confined ourselves to the data on p. 203, appear to show clear evidence of 
limitations of range. For the var. admeta was only taken by the Expedition as a littoral 
form, var. granosimana and var. savignyi at a depth of not less than 20 fathoms. But 
var. savignyt has been constantly taken elsewhere on the shore, and var. intermedia extends 
down to 30 fathoms, and is also taken on the shore’, while of the varieties granosimana and 
admeta we have certainly not sufficient captures to allow of dogmatic statement. 
Again, there is no evidence of any difference in either the habits or the habitat of 
the varieties. In the Island of Minikoi I was able to recognise, besides the type variety 
of 7. admeta, another, differing in the slenderness of the chela, which I suspect to have 
belonged to savignyi (or possibly to intermedia, see the footnote to p. 191). Between the 
type and this variety there appeared to be no difference of habit or habitat. Of course, 
such differences would probably be hard to find, but the negative evidence on this point 
is supported by the results of dredgings in the Maldives. These dredgings supply data for 
recognising the connection, if any exist, between three factors of the environment at least 
and the organisms dredged. The factors are—the nature of the bottom, the presence or 
absence of weed, and the presence or absence of currents bringing water from without the 
1 By the term “ varietal species” I propose to distinguish 2 In this paper the word shore will be used to denote that 
a species in which definite varieties have been recognised part of the littoral belt which lies between tidemarks, includ- 
from a “homogeneous species”’ in which no such varieties ing both the reef and the sand-flats of the lagoon. 
have yet been found. 
