32 



NATURE 



[May 8, 1890 



is in favour of the capture of comets by Jupiter. In fact, 

 the accumulation of these points about / = 192'', which 

 is the longitude of Jupiter's aphelion, may be partially 

 explained by the circumstance that at this point Jupiter 

 as well as the comets move more slowly than at perihelion, 

 hence the sphere of attraction of the planet is sensibly 

 extended, and its action exercised for a longer time on 

 bodies moving in its neighbourhood. 



The similarity of the elements of many comets is very 

 manifest from the above tables, and M. Schulhof dis- 

 cusses in detail the probable identity of such. During 

 last year Mr. Chandler brought forward evidence that 

 Brooks's comet, V. 1889, was identical with the celebrated 

 lost comet of Lexell, and the latter comet has also been 

 asserted to be identical with that of Finlay, VII. 1886, to 

 which it presents many points of resemblance. It is 

 shown in the discussion that, by computing the orbit of 

 Brooks's comet before 1886, the question of its identity 

 with that of Lexell maybe settled, while an extended cal- 

 culation of the perturbations undergone by Finlay's comet 

 indicates that it could not have been near Jupiter in 1779, 

 and hence it is probably not identical with Lexell' s comet. 

 The elements of Finlay's comet are also very similar to 

 those ofVico's comet, I. 1844. In order that the two 

 may be identical, it is necessary that Mars should have 

 augmented the period of Vico's comet by almost two 

 years between 1844 and 1886. 



The elements of Denning's comet present a certain 

 analogy with Pigott's comet, but the two are shown to be 

 certainly distinct. 



Blainpain's comet, 1819, and that of Grischau, 1743, are 

 most probably identical, and the elements of both these 

 present a strong analogy with those of Tempel's comet, 

 so that it is not impossible that this last comet is identical 

 with the other two, or at least with Grischau's comet. 



Whether Coggia's comet, VII. 1873, is identical with 

 Pons's comet, I. 1 818, is not settled. It is interesting to 

 remark, however, that the value of «/ = 0-484, correspond- 

 ing to a period of 5"67 years for Pons's comet, is exactly 

 equal to that of Biela's comet. This, therefore, appears 

 to confirm the opinion that both Biela's comet and that 

 of Coggia represent the debris of an old comet, for, in the 

 case of the division of the materials forming a comet, nj 

 may be regarded as constant for each of the portions 

 detached. 



To decide the question of the identity of Winnecke's 

 with Helfenzrieda's comet, the perturbations undergone 

 by the former t iwards 1800, when it approached very 

 near to Jupiter, have been found, and it is shown that 

 for the identity to ba possible it must have moved faster 

 in its orbit before 1800 than it does now— that is, the 

 period must have been shorter. 



This discussion of cometary identities, coupled with 

 M. Tisserand's elaborate investigations, supports strongly 

 Laplace's hypothesis that comets coming from stellar 

 space, and moving in parabolic orbits, only become 

 periodic by the perturbing action of one of the planets. 

 This theory best explains the origin of the families of 

 comets that cluster round the major planets, and the well- 

 established fact of the disintegration of certain periodic 

 comets, as Biela's in 1846, and Brooks's in 1889. Indeed, 

 such disintegration must eventually happen to all periodic 

 comets. Richard A. Gregory. 



THE JO URNAL OF MORPHOLOG Y> 

 ''pHE issues before us constitute the first three parts of 

 -*• the third volume of this excellent journal. They 

 contain 502 pages with numerous plates and a vast 

 number of woodcuts. The chief contribution in the 

 June number is that of Dr. Macmurrich, on "The 



' The Journal of Morphology, Ti 

 and Co.) 



to December 1889. (Boston: Ginn 



Actinaria of the Bahama Islands." The author's ma- 

 terial was collected during the summer of 1887, in 

 connection with the work of the marine zoological 

 station of the Johns Hopkins University. The mono- 

 graph forms a very valuable contribution to the literature 

 of the Actinice, and it may be regarded as a first step 

 towards a rational comprehension of the tropical members- 

 of this group. It is the more welcome to us at the present 

 juncture, in view of the revision of our native Actinise 

 now progressing, in the hands of H addon and his pupils ; 

 and we cannot but regard the excellent results obtained 

 by Macmurrich as furnishing an additional argument in 

 favour of the advantages of a peripatetic University 

 marine laboratory, as compared with one of fixed habitat. 

 Fourteen species are described, of which three are new. 

 The illustrations are particularly good, and the following 

 distributional conclusion is arrived at, viz. that 

 "so far as the Actinaria are concerned two great areas of 

 distribution can be defined, — the Indo-Pacific, including the 

 Indian and Pacific Oceans and the seas connected with them, 

 such as the Red Sea ; and the Atlantic, including in this the 

 Mediterranean. The Caribbean region of the Atlantic is, how- 

 ever, to be separated from the Atlantic region and united with 

 the Indo-Pacific, the relationships of its Actinaria being very 

 certainly with those of that region." 



Of the remaining papers in the first part, two are by 

 Dr. R. W, Shufeldt, and they treat respectively of" The 

 Comparative Osteology of the Families of the North 

 American Passeres," and of " The Anatomy of Speotyto 

 cwiicularia hypogccaP Both communications are 

 written and illustrated in that peculiar style for which 

 their author is notorious. In the first -named paper the 

 author reverts to his recently expressed 'oelief in a near 

 kinship between the swifts and swallows, but he adds 

 nothing of fresh interest in this debated question. His 

 papers bear the mark of honest work, and we wish them 

 a favourable reception. 



The last communication is one of 8-9 pages upon 

 the "Variation of the Spinal Nerves in the Caudal 

 Region of the Domestic Pigeon," by J. I. Peck. Although 

 short, it is the outcome of a laborious investigation 

 instituted to ascertain whether the spinal nerves vary 

 in the same ratio as the caudal vertebrte, " or whether 

 they remain constant in number and position of exit 

 from the vertebral canal, without reference to the 

 number of vertebrae themselves." One very inter- 

 esting result of the author's investigation is the dis- 

 covery that the coccyx does not diminish in length 

 proportionate to the increase in number of the free caudal 

 vertebrae— on the contrary, it is longest where the said 

 vertebrae are most numerous ; therefore, the detachment 

 of the supernumerary vertebra; from the pygostyle would 

 appear to be due to influences at first productive of a 

 lengthening of the entire caudal region. The interest of 

 this topic is vastly increased, on reflection that the 

 assiduity of a Parker has shown us that our swans and 

 ducklings are the bearers of a tail potentially longer than 

 that of the Saururian, Archasopteryx. 



In the September issue there are two papers, and each 

 is a valuable monograph of its kind. That which will 

 command most attention is the thesis by Prof Cope upon 

 " The Mechanical Causes of the Development of the Hard 

 Parts of the Mammalia." To this subject there are de- 

 voted 150 pages, 5 plates, and close upon 100 most admir- 

 able woodcuts.i The paper is, for the most part, an 

 elaborated resume oi the author's earlier and scattered con- 

 tributions upon the subject under discussion ; and with 



'We wish we could see this author's voluminous treatises invariably 

 illustrated in a manner similarly befittinij their contents. We cannot refrain 

 from comparing the one under review with that on the ' ' Batrachia of North 

 America" recently published under the ausp.ces of the United States 

 National Museum. The illustrations in this are as poor as those referred to 

 above are excellent : carelessly drawn, badly planned, miserably lettered, 

 and in places misleading (if not inaccurate), they " illustra'.e though they 

 hardly adorn" the text to which they are appended, while they render a large 

 portion of the same of little or no avail for working purposes. 



