162 Miscellaneous. 
On Leucochloridium paradoxum and the Development of the Larve 
contained in it into Distoma. By Dr. Ernst ZELLER. 
In this memoir the author gives some new details upon Leuco- 
chloridium, and especially describes the experiments which have led 
him to the discovery of the species of Distomum into which the 
Cercarie contained in this singular nurse are transformed. We 
shall dwell here more particularly upon what relates to the migra- 
tion of this Trematode into its definitive host. 
By keeping some Succinee in confinement Dr. Zeller was enabled 
to observe the growth of the Leucochloridium through their integu- 
ments. It takes about four weeks for a sac to be developed so as 
to become visible in the anterior part of the mollusk, and three 
weeks more for it to acquire its full development. 
When one of the sacs has acquired its full dimensions and moved 
for a certain time in the tentacle of a Succinea, the integuments of 
the mollusk become so thin in this region as to be ruptured by the 
action of a slight pressure from without. When such a rupture is 
produced, the Leucochloridium projects from the tentacle and con- 
tinues for a considerable time to move actively, although still adhe- 
ring at the base by its filiform pedicle. It may be artificially 
detached from the mollusk without the latter seeming to suffer from 
the operation. The Succinea then remains contracted for some 
hours; then it begins again to creep and to take food. If it iskept 
in favourable conditions, another sac may be developed to replace 
that which has been removed. 
M. von Siebold put forward the supposition that the larva (Cer- 
caria exfoliata, Moulinié) contained in Leucochloridium produced 
the Distomum holostomum which inhabits the rectum of several 
marsh birds, such as fallus aquaticus, Gallinula chloropus and G. 
porzana. Dr. Zeller, on his part, observed Succinew infested by 
Leueochloridium in localities where it seemed to him the waders just 
mentioned could not be met with, but which were, on the contrary, 
inhabited by various birds of the family Sylviade. He was thus 
led to suppose that these last might be the true hosts into which the 
Leucochloridium migrated. This supposition seemed to him to be- 
come almost a certainty when he found Distomwm macrostomum, 
Rud., in a redbreast, as the organization of that species is in almost 
complete concordance with that of the larva contained in Leuco- 
chloridium. This Distomum, the organization of which the author 
very carefully describes, has hitherto been observed only in the red- 
breast and some other species of the same group, such as the night- 
ingale, one or two warblers, and two wagtails. All these birds are 
insectivorous, and none of them feed upon mollusks. Dr. Zeller 
supposed that they tore off the Leucochloridium from the tentacles 
of the Succinea, as its resemblance to the larva of an insect is 
striking. To verify this hypothesis he offered to a tame redbreast 
a Succinea containing Leucochloridia which had pushed into the 
tentacles. The bird immediately came down upon one of these 
