98 MR. GARNER ON THE ANATOMY OF THE 
about the sixth of an inch in diameter. The oviducts in the Cyclades open over these 
internal branchie, which are only accessible to the water from behind. Three or four 
of these young animals are inclosed in a membranous case, but the largest are found 
separate, adhering by a byssus. Turton says, that in the month of June he has found 
the young animals of the Kellia rubra containing about twelve perfectly formed young 
ones. In no case does it appear that the ova are discharged from the mouth, as has 
been supposed, nor by the true anus ; nor is there any duct in those which are viviparous 
leading from the ovaria to the interbranchial spaces. 
Diseases and Parasitical Animals. 
As is well known, it is to a disease affecting these animals that we owe the beautiful 
ornament of pearls. The subject of their formation has, however, been exhausted by 
Pliny, Home, Vogt, and many others. Baer has described many of the parasitical 
animals infesting the Conchifera, especially the fresh-water species. The Aspidogaster 
conchicola is very common in the pericardium and excretory organs of the fresh-water 
Muscles. The Nummulella of Carus appears not to be a parasite, but to be formed by 
the rolling on itself of a branchial process. I found the foot of an Anodonta enormously 
distended with parasitic ova, which, when ruptured, were each found to contain several 
young individuals of a species of Distoma. In the foot of another Anodonta I found a 
parasite (Pl. XX. fig. 12.) presenting the following characters. In the mature state 
the body is more or less cylindrical in its shape, but varied much at the will of the 
animal: at one extremity it has two very long appendages, which are spiniferous at 
their terminations, and which in some individuals have a row of round bodies attached 
to one side for part of their length ; these appendages are contracted with great rapidity, 
and are then very short. There is an opening by a circular lip between these append- 
ages. A contraction separates this part, on which they are situated, from the rest of the 
body. There appears to be another opening at the opposite extremity of the animal. 
PLATE XVIII. 
. Animal of the Psammobia florida in its shell. 
. The same exposed. 
. Animal of the Nucula nucleus in its shell. 
. The same, the left valve removed, and the mantle raised. 
. Animal of the Corbula striata in its shell. 
Animal of the Pandora inequivalvis, left valve and part of mantle removed. 
. Left valve of the same. 
. Stomach, intestine, heart, &c. of the Solen ensvs. 
. Stomach, &c. of the Mactra stultorum. 
. Stomach, &c. of the Cardium echinatum. 
Fig. 
BON 
SOMNAMN 
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