434 



NATURE 



[Sept. 4, 1 884 



still doubtful, De Bary classifies the Cliytridece, and 

 Protomyces, and Ustilaginea, all considered as allied 

 phylogenetically with the PJiycomycetcs ; and a series of 

 doubtful Ascomycetes {e.g. Eidam's Helicosporangium j 

 also Exoascus, Saccharomycetes, &c), obviously to be 

 placed next the Ascomycetes proper. Finally, the huge 

 group of the Basidiomycetes, which De Bary regards as 

 connected with the Uredinece, though it is not an easy 

 matter to satisfy one's self of the alliance. 



The rigour with which the literature has been sifted is 

 shown in the references given at the end of each section. 

 There is no doubt that Prof. De Bary may be congratu- 

 lated on once more having written a work which will be 

 a monument to his skill and industry, and a boon to all 

 biologists. 



OUR BOOK SHELF 



A Monographic Revision and Synopsis of /he Trichoptera 

 of the European Fauna. First Additional Supplement 

 (with Seven Plates). By Robert McLachlan, F.R.S., 

 F.L.S., &c. (London: Van Voorst, 1884.) 

 FOUR years ago, in the preface to his very important and 

 elaborate " Monograph of European Trichoptera," Mr. 

 McLachlan promised to continue from time to time the 

 supplemental notices of which the necessity of the case 

 had already caused two to be appended to the original 

 work. The first of these has just (June) been published ; 

 it adds nearly fifty species to those described in the 

 Monograph and its Supplements. Some new forms are 

 noticed to which it has seemed right to assign the rank of 

 varieties, and there is a great deal of additional informa- 

 tion as to localities. While all the species in the original 

 work have been passed under review, in one or two 

 instances those belonging to some genera have been 

 thoroughly revised. Very few new genera are indicated, 

 and the author thinks the time has not yet arrived for a 

 complete subdivision of some of the larger generic groups 

 as now constituted. All but six of the additional species 

 are from within the limits of Europe proper, proving how 

 hazardous it would be to conjecture as yet as to the number 

 forming part of the European fauna. While ready and 

 liberal help has been afforded towards the work of this 

 Supplement by many of the author's friends and corre- 

 spondents, yet it is by one above all the others that the 

 material for it has been accumulated ; for to the labours 

 of the Rev. A. E. Eaton in Italy, Portugal, Madeira, the 

 Canary Islands, and elsewhere, the author stands in- 

 debted for more than three-fifths of the new species, and 

 though Mr. Eaton is well known as an acute, indefatigable, 

 and successful entomologist, does the remark press less 

 home that " if a foreigner making short holiday tours 

 through certain districts previously unexplored (so far as 

 the Trichoptera are concerned) can produce such results, 

 it is needless to call attention to what might be done by 

 residents in the districts " ? 



Among the genera which have been revised we note 

 Sericostoma, which it is now proposed to divide into two 

 groups, i.e. (A) with the Maxillary palpi in the male very 

 prominent and scarcely hairy ; and (B) with the Maxillary 

 palpi in the male slightly prominent and very hairy. 



Additional and valuable information is given concerning 

 the singular forms belonging to the genus Helicopsvche. 

 The author now acknowledges three European species, 

 while he seems to think that the number will yet be greatly 

 increased. The three species at present stand as H. 

 sperata, H. lusitanica, and H. revelieri. The last species 

 equals H. shutileworthii, and was bred in large numbers 

 by M. Reveliere, who found the larva? in very great abun- 

 dance in a stream near Porto Vecchio, Corsica. The 

 imago is to be found all the year round, but it seems to 



require a certain degree of warmth for its emergence, 

 which is always effected in the daytime. The larvae and 

 pupae can exist in a very scanty supply of moisture ; 

 indeed some specimens which were left untended for 

 many days were found quite active though all the water 

 had evaporated from them, and the sand in which they 

 were was only moist. The building material of the helix- 

 like cases is fine sand-grains ; each case forms fully two 

 and a half whorls ; the cement-like substance used to 

 bind the sand-grains together is often applied so thickly 

 that the individual grains are inconspicuous. 



In the genus Setodes, Mr. McLachlan has discovered a 

 character in the posterior wings which (with others) 

 enables the species of the genus as it now stands to 

 arrange themselves into two sharply defined groups (which 

 will be hereafter considered genera). This character is 

 the presence or absence in the posterior wings of a fold 

 above the apical fork known as No. 5. 5. punctata and 

 its allies belong to the group in which the fold is absent, 

 while S. tineiforniis, Curt., &c, belong to the group with 

 the fold. 



This " First Additional Supplement " is illustrated by 

 seven plates engraved from the author's drawings in a very 

 creditable manner by Mr. G. Jarman. As the necessities 

 of the case arise, we are promised a " Second Additional 

 Supplement," which will be as gladly welcomed by those 

 taking an interest in this group of insects as the present 

 one is sure to be. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of rejected manuscripts. 

 No notice is taken of anonymous communications. 



\_7he Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing interesting and novel facts,} 



Lcewy's New Telescope System 



In the June number of the Bulletin Aslronomique there is an 

 important article by M. Lcewy entitled "Description d'un 

 nouveau Systcme de Telescope," on which, with your permis- 

 sion, I would offer some remarks. 



M. Lcewy gives the two possible dispositions or arrangements 

 that allow the principle of the Equatorial coude to be applied to 

 the reflecting telescope. He assumes certain optical and 

 mechanical conditions, and on these treats the question ex- 

 haustively, giving tables showing the different sizes of the 

 mirrors required and other data obtained by the use of formulae 

 based on those conditions. 



The practical difficulties are also dealt with and suggestions 

 made for forms of mountings. There is also a suggestion of 

 the MM. Henry to close the mirrors from the open air by 

 means of a parallel plate of glass to protect them from the effects 

 of dust, moisture, &c. 



This subject has a particular interest for me (as I have no 

 doubt it has also for many others), and I have considered for 

 some time the mechanical difficulties from a different point of 

 view from that of M. Lcewy, coming thereby to conclusions differ 

 ing considerably from those given by him. There is, of course, 

 much to be said on such a subject as this, involving as it does 

 so many points that can be dealt with in so many different 

 ways, and some of these I should much like to say more on by 

 and by ; but at this holiday time of year I will only offer the 

 following observations : — 



1. It is of the first importance to reduce as much as possible 

 the distance (5) between the middle mirror of either optical com- 

 bination or disposition and the focal plane. 



2. By placing the upper bearing of the polar axis below instead 

 of above the cross tube of either disposition, all the mechanical 

 conditions that M. Lcewy has used can be advantageously 

 varied. 



3. The use of the floating polar axis described by me in the 

 May number of the Monthly Notices of the Royal Astronomical 

 Society enables this to be done. 



