60 MYTILID. 
of the ligament, are well developed and of very dark colour. 
The body is the least I ever saw in so large a shell; this is 
occasioned by the ovarium not being mixed up with it, but 
that organ is spread in great thickness over the major part of 
the inside of the mantle on both sides, and at the date above 
noted contains many hundred thousand ova, which at the 
latter part of the autumn are discharged into the sea, leaving 
the mantle a white thin membrane, after which the body of 
the animal increases in bulk and grows fat, becomes edible and 
in season, which is two months later than the oysters, as they 
are not considered good until the end of October. 
They are much eaten at Exmouth by the working people, 
but im some constitutions they have either a deleterious or the 
opposite quality, a pruriginous effect. 
It is a mistake that the ova are received in any part of the 
branchize for protection and maturation for some time pre- 
vious to ejection, as not one-tenth of the immense masses of the 
ovarian membranes could be located there; the branchie, 
from their smoothness, are very ill adapted for such an asylum, 
and if they are ever seen there, it is from the unavoidable 
contact of the ova when in progress of exclusion: the pulli are 
never seen in the animal in a testaceous state, as in the fresh- 
water Unionide, but are at once cast to the waves, where they 
become the prey of various animals; still, enough escape de- 
struction to maintain their enormous numbers. The sea in 
autumn is filled with the ova: at ten miles from land in 14 
fathoms water, if the fishermen’s lobster-pots are left for two 
or three days, they will be covered with very young testaceous 
muscles, and in a week or two more than half an inch long ; 
but the parents never inhabit more than half a mile from the 
shore; of course the ova are floated out to sea, and sink as 
soon as they become testaceous. That the animal never 
carries testaceous pulli is manifest from its bemg more or less 
at all seasons edible. Though this is one of the commonest 
of the bivalves, it is an object of great interest to the mala- 
cologist from its elaborate organization. I may state that this 
is amongst the very few marine Acephala which have the 
ovaria attached more or less to both sides of the mantle; by 
