Fan. 4, 1883 | 
Perihelion Time = Sept. 17'2228200 Greenwich Mean Time, 
Q = 346 1 7°91 
™- 2 = 69 36 12°79 
Z = 141 59 52°16 A 
¢ = 89 7 42°70 1882'0 
log a = _ 1°9331366 
log g = 7°8904739 
period = 793°689 years 
SA cosB = — 006 58 =+0'"or 
x = r[9°99514IT] sin (170 42 12°72 + v) 
¥ = 7 [9°9877234] sin (262 46 57°39 + v) 
= r [9°4435130] sin ( 49 20 25°51 + v) 
The observations as given were afterwards corrected 
for parallax by means of elements previously computed. 
These elements bear a considerable resemblance to 
Comet I., B.c. 371; and it may possibly be its third 
return, a very brilliant comet having been seen in full 
daylight A.D. 363. E. FRISBY, 
Washington, Dec. 19, 1882 Prof. Math., U.S.N. 
a 
THE DUMAS MEDAL 
WE recently (vol. xxvii. p. 174) gave the addresses 
at the Paris Academy of Sciences in connection 
with the presentation to M. Dumas of a medal in com- 
memoration of the fiftieth anniversary of his election to 
the Academy, We are now able, by the courtesy of our 
NATURE 
227 
— 
French contemporary, Za Nature, to reproduce an illus- 
tration of this medal, which was presented by M. Jamin 
in words both eloquent and touching, as a token of the 
“love and gratitude” of the distinguished chemists’ con- 
Jréres, pupils, and friends. The medal is the work of M. 
Alphée Dubois. 
PROFESSOR VON GRAFF’S MONOGRAPH 
ON THE TURBELLARIANS* 
HIS splendid folio monograph consists of two 
volumes, the one comprising the text of over 600 
pages illustrated by woodcuts, the other twenty as beauti- 
fully executed partially coloured plates as have ever been 
turned out, all from the author’s own original drawings. 
The publication of the work has been assisted by a grant 
from the Berlin Royal Academy of Sciences. 
Ludwig von Graff is Professor of Zoology at the College 
of Forestry at Aschaffenburg, in Bavaria. Hs first 
memoir on Turbellarians was published in 1873, at which 
time he first made up his mind to work out from his own 
observation a revision of the Turbellarians. The present 
monograph is, as he tells us in the preface, the result of 
almost incessant work during the last five years. He 
has made numerous journeys to the Naples and Triest 
stations, and has also visited many other parts of the 
European coasts north and south, and the fresh waters 
in all directions, in order to pursue his investigations on 
living Turbellarians. He has thus been able himself to 
examine 70 out of the 168 species of Rhabdoccelida which 
are known with certainty. The work being thus founded 
on so wide a personal acquaintance with the forms of 
which it deals, is of especial weight and value; it consti- 
tutes a systematic monograph of the Rhabdoccelida, 
founded on a sound basis of anatomical structure, and 
embracing all species hitherto described by other observers, 
together with those discovered by the author himself (thirty 
new species). 
It is doubtful whether the present work will be fol- 
lowed by a second part embracing in a similar manner 
all the known Dendroccelida. The matter depends on 
the amount of ground which may be covered by Dr, A. 
Lang’s forthcoming monograph on Turbellarians, in the 
“Fauna and Flora of the Gulf of Naples.” If this mono- 
graph proves to be so comprehensive that a further one 
would be superfluous, then Prof. Graff will publish a 
quantity. of material collected by him concerning the 
Dendrocelida, in three smaller memoirs on the Polyclada, 
the Triclada, and embryology respectively. The present 
work is appropriately dedicated to the memory of O. 
F, Miiller and Sir John Dalyell. It is pleasing to find 
the great merits of the latter thus recognised by a foreign 
naturalist. 
The author does not admit Sidonia = Rhodope varanit, 
which, in opposition to Dr. R. Bergh, he considers to be 
anudibranch, or Dinophilus, which has lately been shown 
to lie near the Archiannelids amongst the Turbellarians ; 
and in the definition he gives of the group excepts the 
Microstomida, which differ from all other Turbellaria in 
having a complete pericesophageal nerve ring, in being 
dizecious, and in multiplying asexually by budding. 
Separating, as is now so usual, the Nemertines alto- 
gether from the Turbellarians, he divides the group into 
the Rhabdocelida and Dendroceelida. In the definition 
given of the two sub-orders, an interesting point of dif- 
ference is brought out, namely, that in the former the 
yelk glands are always present in the form of a pair of 
compact glands, whereas in the latter they are always 
divided up into numerous separate follicles. 
The Rhabdoceelida are divided by the author into three 
groups: I. Acela; 1]. Rhabdoceela; III. Alloiocela, 
which are thus defined :-— 
1 “Monographie der Turbellarien.”” 1. Rhabdoccelida. 
von Graff. (Leipzig: W. Engelmann, 1882.) 
Dr. Ludwig 
