HOM 5 Miscellaneous. 
compilers will be readily met with and corrected under the earnest 
eye of the competent student, who will be too thankful for the aid 
given him in cultivating his special field to find fault with the few 
weeds and stones left on its ready-prepared surface. 


MISCELLANEOUS. 
On the Origin and Distribution of the Turbellaria of the deep Fauna 
of the Lake of Geneva. By M. Dupxessts. 
Ir appears from the author’s researches that all the species of 
Turbellaria from the bottom of the Lake of Geneva are also found 
(with the exception of two very remarkable species, which are at 
the same time the types of new genera) either in the stagnant 
waters of the shores, or in those of the marshes or small lakes of 
other parts of the canton. Nevertheless two reservations must be 
made in this respect: the first is, that many species which are met 
with in the stagnant waters of the country are not to be found in 
the mud of the deep waters; the second is, that the greater number 
of species which live also at a great depth have undergone some 
easily appreciable modifications. 
Speaking first of the Dendroccelous Turbellaria or Planarians, the 
author describes the modifications which are observed in Dendro- 
celum lacteum and fuscwm on comparing the individuals of the 
shores with those which inhabit the depths of the lake. The speci- 
mens coming from great depths are generally smaller and lighter in 
colour, and are further distinguished by the rosy colour of the 
digestive tube. The visual organ tends to become atrophied; one 
of these varieties of D. lactewm is remarkable for the division of 
each oculiform point into two smaller parts, and has been described 
by M. Griiff under the name of Planaria quadrioculata. 
Other species, such as Planaria gonocephala, so common in the 
rivulets of the Jorat, never descend so far as the lake; and it is the 
same with the numerous representatives of the genus Polycelis. 
Usually the Planarie of the deep fauna appear to have emigrated 
from the waters of the shores; but this group is represented at the 
bottom of the lake by a smaller number of species. 
Some very similar facts strike us in the distribution of the Rhab- 
docela. Typhloplana viridis and T’. subfusca, which occur every- 
where in the stagnant waters of the country, are also met with in 
the depths of the Lake of Geneva, while 7’. pellucida and 7. pallida, 
so common in the pools, have not yet been seen in the mud of the 
lake. 
Regarding the Vorticine, Mesostomum Ehrenbergit, lingua, and 
pusillum are found both in the shallows and depths of the lake, while 
M. personatum appears, on the contrary, to be absent in the latter. 
A curious type, Microstomum lineare, which is met with every- 
where on the shores, descends also to the deep waters of the lake ; 
but it there invariably becomes larger, and its intestine of a pale 
rose-colour similar to that of the Planarie. 
