114 A HISTORY OF RECENT CRUSTACEA 
which belong to Great Britain and are also extensively dis- 
tributed in the North Atlantic. These are Hyas araneus 
(Linn.) and Hyas coarctatus, Leach. In a tiny specimen 
of the latter species, taken from off the carapace of the 
mother, small spines or tubercles are observable on both 
sides of each of the two divisions of the rostrum, on the 
outer side of the second antenne, and on the eye-stalks. 
These minute characters do not reappear in the adult. 
The two species mentioned are very abundant on the coast 
of Sweden, and Aurivillius found that they were almost 
without exception dressed up either in pieces of different 
algze (almost always Floridez) or of shallow-water sponges, 
or with Hydroids, tubicolous Annelids, Polyzoa, Cirri- 
pedes, or Ascidians simple or compound. His experiments 
showed him that, if some of these settled rather by the 
crab’s permission than its active interference, yet they had 
been originally under its control, while in most cases the 
colonists had been actually planted and forced at the will 
of the crustacean to occupy their several stations. He 
found, just as Mr. David Robertson of Cumbrae had done, 
that his specimens of Hyas were capable not only of dress- 
ing but of undressing themselves. Of the effectiveness of 
their disguises he had often had practical experience, when 
upon visiting his aquarium in the morning he was unable 
to find specimens which he had placed there overnight, 
and which he at first thought must have escaped. Close 
inspection and the help of a magnifying glass, however, 
would always show that they were present, but that they 
had so decked themselves out with the vegetables and 
animals around them as to lose all invidious prominence. 
By transplanting into an environment of sponges some 
that had clothed themselves in bright-coloured alge, he 
ascertained how accurately they knew their business, for 
they laboriously picked off the gay colours, and stuck 
themselves over with fragments of sponge in their place. 
The chelipeds of these crabs are adapted by length and 
by the flexibility of the joints to reach to the different parts 
of the body which require dressing up. The hooks and 
hairs which hold on the tags and patches have been already 
