Experiments on the Development of the Liver-Jiuke. 13 
that of Julianshaab, on the west coast of Greenland — is likely 
to prove instructive, its absence from Iceland may also throw 
some light upon the subject. Most or all of the mollusca 
which have been or can be supposed to act and suffer as 
Zioischenivirth for the Fasc.iola are to be found in Iceland, viz.. 
Avion ater, Arion horiensis, Limncea truncatula and Limncea 
peregra* as well as Planorbis rotundatus, if not Planorhis mar- 
ginatns. And that abundant opportunities for the introduction 
of Fasciola hcpatica into Iceland have been given by the 
importation of sheep from abroad is learnt from what Olafsen, 
I.e., ii. pp. 198-199, tells us as to the ascription of another sort 
of sheep disease to such importation. 
I incline to ascribe this immunity from rot which the sheep 
enjoy in Iceland to the habit which they in common with the 
Shetland and Orkney sheep have of feeding between high- and 
low-water marks upon the seaweeds specified by Olafsen in 
various passages, q.v., I.e., i. 233,279, ii. 198, and Low, 'Domestic 
Animals of Great Britain,' p. 59. The Fasciola hepatica is a 
freshwater animal, and would not of course be picked up in 
such a locality as the interval between " Ebbe and Fluth," to 
which the sheep resort even on the dark nights of winter. It 
is possible to speculate as to the virtues of salt as an anthel- 
minthic, and to suggest that it may act either by enabling a 
better gastric juice to be secreted, and so giving the sheep a 
better chance of digesting the larval faseiolce when swallowed, 
or by provoking a more copious flow of bile, and so washing 
the young fluke out of the gall-ducts. This, perhaps, is not the 
place for such enquiries. But it is a pure natural history fact 
that localities rich in deposits of salt are favourable to the 
growth and health of sheep. Pallas, in the wonderful eleventh 
Fasciculus of his ' Spicilegia Zoologica,' dwells on this in re- 
ference to the Steatopygous variety of the domestic sheep at 
pp. 65-67, and with reference to the Argali, the Ovis fera 
Siberica, supposed to be the parent stock of Ovis aries, var. 
domestiea, he writes thus at p. 12 : " Omni vero tempore ubi 
possunt loca salsagine rorida quibus universa Siberia abundat 
crebro frequentant, terramque sale fcetam cavant quod cervino 
quoque generi solemne est." 
George Rolleston. 
June 25, 1880. 
3. Experiments with Embryo. — The first experiment made was 
with Arion ater and Lhnax agrestis. A piece of turf was spread 
at the bottom of a large aquarium, and a quantity of sheep's 
* See Mcircli, ' Fauuula MoUuscorum Islandise,' 1868, pp. 12 and 16. 
