932 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. XXVIII. 
ophiuroids are extremely conspicuous on such hosts, these must tend to be 
picked o£E by those animals that feed upon them ; this must give such an ad- 
vantage to those strains that produce a majority of dark coloured offspring that 
there can be little doubt that here we have a distinct variety in the making, 
whereby a strain will be formed producing none but dark coloured young to 
Jive on a similarly coloured host. 
Masking among Indian Crabs, 
The habit of certain crabs to seek safety by masking their body with weeds 
and sponges and other organisms is well known ; the spider-crabs of the fa- 
mily Maiidae, the velvet crabs (Dromiidae), and the various species of the sand- 
crab Dorippe, are those that have developed this habit to its greatest extent. 
They adopt two principal methods ; the first, employed by the spider-crabs, is 
by trimming the carapace and often the larger legs, with fragments of seaweeds, 
sponges, zoophytes or ascidians, which are held in position by being hooked on 
recurved hairs developed for this purpose, and not found on any other kind of 
crab. The smlace of the carapace in these crabs is very rough, usually raised 
into numerous low conical tubercles ; these assist in heightening the disguise 
ana in one case, where I had a number ot the large English Maia squinado in 
confinement (Jersey) in a tank bereft of seaweeds, the crabs in lieu of anything 
better adapted to the purpose, selected suitable pebbles and balanced them 
carefully among these tubercles. The second method, that of the various 
genera of the Dromiidse and Dorippidse, is to hold either a mass of some im- 
attraetive sessile animal or a flattened shell over the back as a concealing cloak; 
to this end the hinder legs, either one or two pairs, are employed, and specially 
modified both in jointing and in the form of the terminal joint. This last in 
these crabs is sharp and exactly suits its purpose of being hooked into the sub- 
stance of the concealing sponge or ascidian in the case of the Dromiidse ; in the 
Dorippidae the two last joints are still further modified so that they form a 
fairly perfect hook, pecidiarly well adapted to grasp the thin edge of a shell held 
aloft over the body. (Figs. 2 and 5). 
Fig. 2 . — Dorippe facchino stripped of its masking organism, to 
show the two pairs of specialized thoracic limbs with 
their terminal hooked joints. (Original.) 
In the weedy shallows of Palk Bay, a small stoutly built spider-crab, Halimus 
sp.. is fairly common. After the manner of its kind it usually decorates its 
