Febbtjaet 26, 1909] 



SCIENCE 



349 



(p. 39) the older young, which have attained 

 a length of over an inch and may be several 

 weeks, or even months, old. 



It might appear hypercritical to raise the 

 question whether the walking legs of a 

 higher crustacean like the crayfish have claws 

 (p. 23). Huxley got around this difficulty 

 by using the terms " double " and " single 

 claws " for the forceps of the first three and 

 the " nails " of the last two pairs of legs, 

 respectively, which describe the conditions 

 met with in the crayfish exactly. This, how- 

 ever, does not correct the inappropriate though 

 technical use of the Latin word chela for the 

 pincers alone. 



It is certain that metamorphosis in the 

 higher crustacea has been reduced or elimi- 

 nated under very different conditions in the 

 rather numerous cases in which a reduction 

 has occurred, as seen not only in the common 

 lobsters (Homarus'), but in many deep sea 

 shrimps, shallow water Alphei and terrestrial 

 crabs (Gegarcinus}. As regards the possible 

 influence which conditions of life in fresh 

 water may entail, it is interesting to note that 

 metamorphosis has' been practically elimi- 

 nated, not only in the fluviatile crayfish, but 

 also in Palwmonetes varians of Europe and in 

 P. exilipes, of parts of the eastern United 

 States, one of the few fresh-water genera of 

 prawns known, and that in this case their 

 immediate marine ancestor, the common little 

 PalcBmoneies vulgaris, has a metamorphosis 

 both long and complete. 



Francis H. Herrick 



Astronomy of To-day. By Cecil G. Dolmage, 

 F.E.A.S. Pp. xvi + 363, with 45 illustra- 

 tions and diagrams. Philadelphia, J. B. 

 Lippincott. 1909. 



The fascination of astronomy seems as 

 Strong to-day as in the distant past, when 

 some knowledge of the heavens was essential 

 to the every-day life of the traveler and the 

 householder. To-day the compass, not the 

 pole-star, guides the voyager across the seas 

 and deserts; the watch and the calendar have 

 replaced as timepieces the sun and the con- 

 stellations, yet the interest in matters astro- 



nomical never wanes. To a large extent this 

 interest is due to the ever-widening fields of 

 astronomical research. Fifty years ago as- 

 tronomy was practically confined to a mathe- 

 matical explanation of planetary motion, with 

 a few dry statistical facts concerning the size, 

 shape and mass of the various bodies. To- 

 day astronomy deals with the bodies them.- 

 selves, with their physical conditions, their 

 life histories, and the probable stages of their 

 evolution. Physics and chemistry are the 

 tools with which an astronomer of to-day 

 works, photography and the photographic 

 plate have replaced the eye and the hand in 

 picturing the wonders of the heavens. Now 

 this new astronomy appeals more directly to 

 the popular reader than did the mathematical 

 astronomy of the past century: one is more 

 interested in knowing what a body is and how 

 it came into being, than in learning the 

 minute details of the path it is describing. 

 That such is the case and that the interest in 

 things astronomical is general, is evidtenced 

 by the increasing number of popular and 

 non-technical books on various astronomical 

 subjects. 



The field of astronomy to-day, however, is 

 so broad, it covers so much ground, that it 

 can hardly be adequately treated of in a 

 single small volume. The space in even a 

 large book hardly suffices to give proper ac- 

 count of a single minor division of the great 

 science. A single volume, which attempts to 

 cover the entire field, can be but little more 

 than a general index, pointing out to the 

 reader the divisions of the subject, the rela- 

 tive importance of each, sketching in a broad 

 way the principal facts and the underlying 

 theories of celestial development, and indi- 

 cating who the real workers are and where 

 special details and facts can be obtained. 



Now in some of these particulars the well 

 got up and attractive book of Mr. Dolmage 

 falls short of what such a book might be. If 

 we regard the amount of space devoted to a 

 subject as indicating to a certain extent the 

 importance of the subject, then this volume 

 shows some rather remarkable conceptions. 

 For us the sun is undoubtedly the most im- 

 portant body in the heavens, it is the center 



