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 NH« 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 C0 2 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- 



PEiNSORIUM OF THE BEE. 



Prof. George Macloskie, 01 Princeton, N. J. 



The endocranium of insects is produced by infoldings 

 of the cranial wall, and although several groups (as 

 Diptera, Hemiptera, 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- 

 lev's description of this in his Anatomy of the Invertebrates 

 is inaccurate.) 



lhe 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- 

 iliac, and upon it is an anterior pair of bars supporting 

 the labium. In its working, this frame-work embodies the 

 principle of a recent patent for producing steady ryoticn. 



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 floorof 

 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. 



spectrum of each has been examined by inserting a prism 

 between the objective and eyepiece of the large telescope. 

 A star 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 ordinarv eve-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 1S63 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 

 barelv allowed time for its identification. It proved to be 

 the star known as Oeltzen 176S1, and must therefore have 

 had nearly its present brightness forty years ago. 



The field for discover}- by the method here given is far 

 from being exhausted since, less than one hundreth part of 

 the heavens has as vet been examined. 



ON LAND SNAILS OF THE PALEOZOIC PERIOD. 



By Dr. Dawson, F. R. S.. Princ'p.d of McGill University, 

 Montreal. 



The land snails occurringin 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 Strop kites 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 closel} - 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 materia] filling a hollow Sigillaria, by Sir Charles Lyell 

 and Dr. Dawson in 1S51. 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. 



NEW PLANETARY NEBULA. 



By PSOFESSOB Pickering. 



Ik- described the observations of the planetary nebulae, 

 are now in progress at the Harvard College Obser- 

 vatory. Besides measuring the light of these bodies, the 



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 otiier 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 deeipiens), are given, and five new 



