162 Miscellaneous. 



On Lcucochloridium paradoxum and the Development of the Larvee 

 contained in it into Distoma. By Dr. Ernst Zeller. 



In this memoir tho author gives some new details upon Leuco- 

 chloridium, and especially describes the experiments which have led 

 him to tho discovery of the species of Distomum into which the 

 Cercarict contained in this singular nurse are transformed. "We 

 shall dwell hero more jvirticularly upon what relates to tho migra- 

 tion of this Trematodc into its definitive host. 



By keeping some iSncclneie in confinement Dr. Zeller was enabled 

 to observe the growth of the Leueochloridimn 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 tho mollusk, aud tliree 

 weeks more for it to acquire its full development. 



When one of the sacs has acquired its full thmeusions 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 tho 

 action of a slight pressure from without. When such a rupture is 

 produced, the Leueochloridimn 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 is kept 

 in favourable conditions, another sac may be developed to replace 

 that which has been removed. 



M. von 8iebold put forward the supposition that the larva (Cer- 

 cana cxfoliata, Moulinie) contained in Lcucochloridium produced 

 the Distonium holostoinum which inhabits the rectum of several 

 marsh birds, such as liallas aquaticus, Gallimda chloropus and O. 

 2>or:ana. Dr. Zeller, on his part, obsers-ed Succinece infested by 

 Leucochloridium in locahtics where it seemed to him the waders just 

 mentioned could not be met with, but which were, on tho contrary, 

 inhabited by various buds of the family Sylviadso. He was thus 

 led to suppose that these last might be the true hosts into which the 

 Leucochhridi\im migrated. This supposition seemed to liim to be- 

 come almost a certainty when he found Distornum 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 Distornum, the organization of which the author 

 very carefiilly 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. AU these birds are 

 insectivorous, and none of them feed upon mollusks. Dr. Zeller 

 supposed that they tore ofi' 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 Siiccinca contaiiiing L(ucorhh)ridi<i which had pushed into tho 

 tentacles. The bird immediately came down upon one of these 



