568 



NATURE 



[April 13, 1899 



A TREATISE ON SPINES. 



A 



SERIES of papers upon "The Origin and Significance 

 of Spines : a Study in Evolution," contributed by Dr. 

 C. E. Beecher to the American Journal of Science from July 

 to October last, has now been distributed by their author 

 in a collected form. There are 80 pages in all, with 73 text 

 illustrations, tables, and a plate delineating leading types of 

 Radiolarian spines after Haeckel. Under the head of "spines" 

 (here are dealt with objects between and including " the 

 modified hairs of the .ffi/z/V/Ha and Porcupine," and "the pro- 

 jecting rays and processes of Radiolaria " ; movable and fixed 

 forms are alike passed in review, horns and antlers come in for 

 consideration, and only such " spines" appear to be disregarded 

 as are "distinctly internal structures." 



The author has been at immen.se pains to bring together all 

 that is known concerning the nature, origin, laws of growth and 

 limitations of spines, not excluding those met with in the 

 vegetable kingdom ; and while, in arranging in an orderly 

 manner this vast accumulation of facts, he has done a good 

 service, we venture to think that the utility of his essay 

 is, to a large extent, marred by the too sudden diversion into 

 side topics which at times appear to us irrelevant. The " law 

 of variation," according to Cope ; that of " multiplication 

 of effects," according to Herbert Spencer ; the principle of 

 "localised stages of growth," by Jackson; of "reproductive 

 divergence," by Vernon ; with "sexual selection," and other 

 supposed laws and heresies, are all in turn called in for com- 

 ment and consideration. The author so flits about among 

 extremes concerning both organs and doctrines under review, 

 that the reader is often at a loss to discover his views and 

 arguments, and at what he is sometimes aiming. Of all his 

 theses, that which he seems to us to have best substantiated is 

 expressed in his concluding remark that "after attaining the 

 limit of spine differentiation spinose organisms leave no 

 descendants, and . . . that out of spinose types no new types 

 are developed." The subject of "spines" is a notoriously 

 fascinating one upon which much has been written. On 

 perusal of the excellent list of references which accompanies 

 the papers, and comparison with the text, the author appears to 

 us to have exercised too little discrimination in his reading, and 

 to have been too prone to accept much which he found in print. 

 Some of his allusions to the fishes and the desert plants appear 

 especially open to this objection. His reputation is now so well 

 established among working zoologists, in connection with his 

 recent magnificent investigations into the phylogeny of the 

 Brachiopoda and the structure and systematic position of the 

 Trilobites — achievements of which even Vale College Museum 

 may well be proud — that his present series of papers will be 

 widely read. While we are profoundly thanklul to him for hav- 

 ing collected together and arranged in a workable form so 

 instructive an amount of detail, we doubt if some of his con- 

 clusions will prove any more convincing to the majority than 

 those which three years ago ltd him to a belief in the so-called 

 Protaspis larva. 



FOSSIL JELLY-FISH. 

 A N elaborate work on Fossil Medusie, by Mr. C. D. 

 ■"■ Walcott, forms the thirtieth volume of the Mono- 

 graphs of the United States Geological Survey. The attention 

 of the author was first directed to the occurrence of certain 

 siliceous nodules, known as "star-cobbles," in the Middle 

 Cambrian shales of .Alabama ; and after coming to the conclusion 

 that these nodules contained fossil Medusie,he was led to extend 

 his researches to all the known fossil forms. Among these 

 some had been recognised in Sweden by Nathorst, and in 

 Bavaria by Haeckel ; and the full record embraces forms from 

 the Cambrian of the United States, Sweden, Russia, and 

 Bohemia ; from the Permian of Saxony ; and from the Jurassic 

 of Bavaria. 



The author points out that, under certain conditions, when a 

 Medusa is overwhelmed by muddy sediment, it may retain its 

 shape sufficiently long for the sediment to solidify and make a 

 mould of its external form. Plaster-casts of certain jelly-fish 

 may in some instances be readily obtained. The most favour- 

 able conditions for the natural preservation of a Medusa appear to 

 be by burial and rapid consolidation of sediment beneath water ; 

 but the author observes that not one in a hundred of the fossil 

 specimens, shows traces of any structure within the body, and, 



NO. 1537, VOL. 59] 



so far as is known, the particularly favourable conditions 

 required " were confined during geologic time to the vicinity of 

 the spot in the Cambrian sea that is now occupied by the town- 

 ship of Cedar Bluff, Cherokee County, Alabama." There the 

 nodules with Medusa: occur in finely laminated shales, and 

 much of the silica forming the nodules appears to be original, 

 and derived from the solution of siliceous organisms. The 

 Medusa; lived in relatively shallow water, and weie quickly 

 overwhelmed and buried in a siliceous mud that was subse- 

 quently consolidated to form a siliceous shale. The silica, 

 which forms a large portion of the shale, was proliably derived 

 from detrital quartz. 



The author discusses the relation of the Medusa; to the 

 Sponges, and more especially of the Middle Cambrian forms ; 

 and he then proceeds to describe the various species, which are 

 illustrated in forty-seven plates. These figures will prove of 

 considerable interest to geologists'; they serve to draw attention 

 to many curious and hitherto problematical structures ; and may 

 lead to more precise information with regard to their mode of 

 occurrence. There appears to be no doubt that some of the 

 forms, even of Cambrian age, are true Medusa: ; and the author 

 believes that at this early period, if not in pre-Cambrian times, 

 tlie acraspedole Medusae were mainly diflerentiated. He 

 remarks, however, that we have yet much to learn about the 

 medusiform ancestors of the Hydrozoa. 



SEASONAL DIMORPHISM IN 

 LEPIDOPTERA.' 

 T HAVE thought this to be a suitable subject for my address, 

 because it is not only of high interest as a remarkable 

 phase of variation, but has also of late years been brought 

 prominently to notice by the researches of two groups of 

 entomological observers ; firstly, those who, like the pioneers, 

 G. Dorfmcister, W. H. Edwards and August Weismann, have 

 experimentally studied the effects of high and low temperatures 

 artificially applied to lepidopterous pupx of European or North 

 American species ; and secondly, those who have noted the 

 seasonal changes in butterflies occurring naturally in various 

 tropical and subtropical regions, and have in some cases reared 

 one seasonal form of a species from ova deposited by the other. 

 The earlier temperature experiments in Europe and North 

 America were long in advance of the observations on seasonal 

 dimorphism in tropical countries, the latter indeed being the 

 natural outcome of the former. It may prove not uninteresting 

 if I briefly pass under review the published memoirs relating to 

 both sets of oKservations, but, as regards the temperature 

 experiments, limiting my remarks almost exclusively to those 

 relating to .seasonally-dimorphic species. 



No doubt many of us remember with what interest we 

 welcomed Weismann's able treatise- published twenty-three 

 years ago, whether in the original or in the English edition 

 (translated by Prof Meldola) issued in 18S2. The cases known 

 to Weismann, and described in this memoir, were not 

 numerous ; he calls special attention to six European cases 

 (Araschnia levana, Lycaena amynlas, J., ageslis, Chrysophanui 

 phtaeas, Pieris napi, and Euchloe belia), and to three North 

 American ( Pliyciodes tharos, Grapta iuterrogalionis and Papilio- 

 a/a.r), the latter known to science through the investigations of 

 VV. H. Edwards, the well-known monographer of the butterflies 

 of North America, whose experiments and results* are re- 

 published with .additions as Appendix II. to Weismann's essay. 

 In the phenomenon of seasonal dimorphism Weismann recog- 

 nised, as two prominent factors in the possible dirtwf influence 

 of the varying external conditions of^ life, temperature and 

 duration of the pupal period ; and his experiments with 

 Araschnia levana and Pieris napi were accordingly carried on 

 with the view of ascertaining whether the dimorphism exhibited 

 by those species could be traced to the direct action of those 

 factors. In the case of A. levana, he first subjected the pupx 

 obtained from eggs laid by the winter form, immediately after 

 pupation, to artificial low temperatures, and the rcsKit was that, 

 by exposure to temperature of o"-l° R. for four weeks, three- 



> An address re.td l>cfore lt)e Knlofnoloeical Society of London at ihe 

 annual mccling on January 18, by KoUnd Trimen, K R.S., President of 

 the Society. 



3 " Sludien rur t^escendcnz-lheoiie. 1. Ucber den Saison-Dimorphis- 

 mus der SchmctlcrliiiKe," 187$' 



» Caiut/iaK Enlfmolcfist, vii. p. 336(1875), and ix. p. 69(1879). . 



