136 
SCIENCE. 
It will be seen from these tables that the effect of ammo- 
nia gas in solution upon the water absorbing it is to in- 
crease greatly the co-efficient of expansion and to lower 
very rapidly both the points of maximum density and of 
freezing. 
In these respects the gas acts just as a salt in solution 
would do. Gas solution and salt solution would seem to 
be closely related phenomena, each resulting in the forma- 
tion of a mixed liquid, viz : of a liquid composed of two sets 
of independently moving molecules. 
The effect of ammonia gas upon the volume of the water 
absorbing it is expressed by the following law : 
When it is absorbed by water , the increase in volume for a 
constant temperature is directly proportional to the amount of 
gas absorbed. 
This may be shown to be for NII ;) gas in water by 
plotting a set of curves with the volumes given in the 
above tables as ordinates and percentages of gas as 
abcissae. These curves, whatever temperatures be chosen, 
resolve themselves into straight lines. Since for the case 
of CO, gas in water the same law had been already found 
.true by direct measurement of the change of volume due 
to the absorption of the gas at constant temperatures, we 
are warranted in suspecting the law to be a general one. 
THE ENDOCRANIUM AND MAXILLARY SUS- 
PEmSORIUM OF THE BEE. 
Prof. George Macloskie, of Princeton, N. J. 
The endocranium of insects is produced by infoldings 
of the cranial wall, and although stveral groups (as 
Diptera, Ilemiptera, Coleoptera, Lepidoptera,) have 
been represented as devoid of such structures, Prof. 
Macloskie finds an endocranium present in all these 
orders. The posterior or epicranial part of the skull has 
no internal processes; The clypeus, or “face,” has 
a thick posterior ridge (just in advance of the antenna:). 
From this ridge descend, in bees and allied insects, two 
meso-cephalic pillars, reaching to the floor of the cranium, 
in front of the great foramen. These two pillars support 
the roof of the skull. They occur, with variations, in squash- 
bug, gadfly, mosquito, butterfly, and dragonfly. In the 
cockroach they take the form of a perforated plate, being 
united anteriorly by a cross-bar (which binds the mandibles 
together), and being webbed excepting at the centre. (Hux- 
ley’s description of this in his Anatomy of the Invertebrates 
is inaccurate.) 
The maxillae and labium of the bee are supported by a 
long framework with elbows and hinges. This suspen- 
sorium is incorrectly represented in published figures. It 
is, in part correctly figured by Wolff, who misinterprets it 
(as if it were on the type of the mammalian skull). Its 
basal or posterior rods are attached close to the great for- 
amen and to the base of the meso-cephalic pillars, and they 
are united by a thick web to the base of the skull. The 
mid-segment, consisting of a pair of bars, supports the max- 
illae, and upon it is an anterior pair of bars supporting i 
the labium. In its working, this frame-work embodies the 
principle of a recent patent for producing steady motion. 
The methods by which the maxillae and labium are pro- 
truded and withdrawn were described, also the relations 
and mode of working of the pharynx-parts in the mouth. 
The discovery of a double set of salivary glands was report- 
ed ; a cephalic set supplying the inner tongue on the floor of 
the mouth, and the thoracic glands, sending their long duct 
forward to the labium. The inner structure of the bee’s 
head was shown to be of the same pattern as in other in- 
sects, though varied in details. The paper was illustrated 
by diagrams and microscopic preparations. 
NEW PLANETARY NEBULAE. 
By Professor Pickering. 
He described the observations of the planetary nebulte, 
are now in progress at the Harvard College Obser- I 
vatory. Besides measuring the light of these bodies, the I 
spectrum of each has been examined by inserting a prism 
between the objective and eyepiece of the large telescope. 
A sta. is converted into a colored line of light, but the 
nebulae, being nearly monochromatic, appears as a bright 
point. The difference is so marked that the idea suggested 
itself that by this means planetary nebulae might be discov- 
ered, whose disks are so small that they can not otherwise 
be distinguished from stars. A search was accordingly 
undertaken on the evening of July 13th, by sweeping or 
moving the telescope so that a great number of stars could 
be examined in a short time. In a few minutes such a 
nebula was found, which with an ordinary eye-piece might 
readily be mistaken for a twelfth magnitude star. A similar 
object was also detected on the next evening. After this, 
sweeps on several evenings failed to reveal any new nebulae, 
although it is estimated that the spectra of over a hundred 
thousand stars were examined. 
On night before last, while continuing this work, an object 
with a remarkable spectrum entered the field. The light 
appeared to consist mainly of a band in the green, a line in 
the red and probably a fainter band in the yellow, the whole 
being superposed on a faint continuous spectrum. The 
new stars which blazed out in Corona in 1863 and in Cyg- 
nus in 1876, presented for a short time a similar spectrum, 
but with this exception the star noted above appears to be 
unique. It is too soon to form a theory regarding the nature 
of this body, as clouds interrupted the observations and 
barely allowed time for its identification. It proved to be 
the star known as Oeltzen 17681, and must therefore have 
had nearly its present brightness forty years ago. 
The field for discovery by the method here given is far 
from being exhausted since, less than one hundreth part of 
the heavens has as yet been examined. 
ON LAND SNAILS OF THE PALAEOZOIC PERIOD. 
By Dr. Dawson, F. R. S.. Principal of McGill Universiiy, 
Montreal. 
The land snails occurring in the carboniferous and Devo- 
nian systems, of which six species are known, were no- 
ticed in detail. Two of these, Pupa Bigsbii from the coal 
formation of Nova Scotia, and Strophites grandava from the 
Erian (Devonian) of St. Johns, New Brunswick, were de- 
scribed for the first time. Four of the known species 
belong to the different subdivisions of the old genus Pupa , 
and two are helicord or snail-like in form. They constitute 
a very isolated group of fossils, as none are known in older 
formations, and there are none newer till we reach the early 
Tertiary. Though all of somewhat distinct types, they all 
belong to one great family or sub-order of the Pulmonifera , 
and are all closely allied to types still living. All the 
species hitherto found are American, four being found in 
Nova Scotia and New Brunswick, and two in Illinois. 
The latter were discovered and described by the late Mr. 
Bradley. Pupa vetusta , the earliest known, was found in 
the material filling a hollow Sigillaria, by Sir Charles Lyell 
and Dr. Dawson in 1851. In the paper, which will proba- 
bly appear in full in the American Journal of Science, 
figures and descriptions of all the species are given, and 
their affinities and mode of occurrence are discussed. 
FURTHER NOTES ON THE POLLINATION OF 
YUCCA AND ON PRONUBA AND PRODOXUS. 
By C. V. Riley. 
The author refers to the original paper on the Fructification 
of Yucca read at the Dubuque (1872) meeting of the Associa- 
tion and notices various criticisms since made upon its con- 
clusions. The paper shows that none of these criticisms were 
warranted, and verifies the original observations and conclu- 
sions by subsequent experience. It points out the causes of 
error in that other writers have confounded related moths 
having similar general appearance but great structural differ- 
ences and different habits. The characters of the Bogus 
Yucca Moth ( Prodoxus decipiens), are given, and five new 
