352 ASELLIDA. 
Tue GRIBBLE is one of the most destructive creatures 
to be found amongst the whole of the articulated animals, 
burrowing into the wood of marine erections, such as 
piers, piles, and other works of public utility. Being the 
only known species contained in the genus, its leading 
characters have been detailed above, and in the generic 
description. The male is about one-third larger than 
the female. In general, not more than seven, or at most 
nine, young ones are found within the incubatory pouch. 
When the animal is alive, it contracts itself almost into a 
ball, thus confirming the relationship of the genus to the 
Spheromide. They are able to live at least a fortnight 
within the wood, taken out of the water and placed in a 
dry room. Each of the eyes is composed of seven or 
eight blackish facets, one being in the centre. The legs 
are articulated just beneath the sloping lateral margins of 
the body, and being partly folded beneath the pereion, a 
small portion only of each is seen when the animal is in 
motion. ‘The longest are the first and fifth pairs; the legs 
of the second segment are shorter and thicker than those 
of the first, the third and fourth pairs being similar to 
the second; the fifth pair is more slender, and the sixth 
and seventh pairs resemble the fifth, but are rather 
smaller. The terminal finger is, in all the legs, single and 
somewhat hooked. 
Dr. Coldstream describes a peculiar organ situated 
within the cavity of the tail, behind the branchiz, con- 
sisting of two vesicular bodies of an oval form, attached 
toa common peduncle. They were always found filled 
with numerous dark-coloured granules, of an irregularly 
round shape, which could not be detached from the sub- 
stance in which they were embedded by tearing it up. 
They exist in both males and females. The animal creeps 
but very slowly, backwards as well as forwards, appearing 
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