Oct. II, 1877] 



NATURE 



503 



siucincti — AnlJiMhai-is cardamiiies — with the following results : — 

 In seven instances I tut the loop (and sometimes a second one) 

 which the caterpillar had spun ; and in all the chrysalis was 

 excluded without falling down ; but in no case was the tail of 

 the chrysalis withdrawn from the pocket of the old caterpillar- 

 skin, so that its suspension is direcily from the latter. In eleven 

 cases in which I did not inter ere, only two chrysalids were 

 excluded in the normal wav, i.e., vertically, with the head up, a 

 girdle round the inSfCt and the chtysalis-'ail withdrawn from the 

 old skin and attached immediately to the silk on the stem of ihe 

 plant. In three other cases in which a loop was spun by the 

 caterpillar, the chrysalis seems to have turned upside-down during 

 exclusion, the tail being now uppermost, the ioaf> tivisUd.^ and 

 the hooks fastened in lud.se silk upon the plant-siem. Six cater- 

 pillars either spun no loon at all or one so insufficient that they 

 became .•?/j;^fV/j2 of themselves before exclusion began, and were 

 all but one (which fell down) successfully excluded in thi> posi- 

 tion — the tail of the chrysalis, however, being still retained wiiliin 

 the pocket of the old skin. 



The most interesting and curious point in the trans rormation 

 of a caterpillar of the suspctisi is the manner in which Ihe newly- 

 excluded chrysalis is kept from falling, while its hook-furnished 

 tail is being withdrawn from the old skin of the caterpillar and 

 made fast in the cone of silk to which the latter was attached. 

 I am ignorant whether any other explanation of this process has 

 been given than that, I believe, orjginally communica'ed by 

 Reaumur and detailed in Kirby and Spence, vol. iii. pp. 20S- 

 209, and repeated in such recent works as Figuiei's "Insect 

 World," from the English edition of which work by Prof. P. 

 Martin Duncan (1872), p. 148, I quote the following account of 

 the pupation of K(7ttf.fja ?^r//V«r .• — *' But here comes the culnr,i- 

 nating point, the most difficult part of ilie operation. The 

 chrysalis, which is shorter than the caterpillar, is at some 

 distance from the silky network to which it must fix itself; 

 it is only supported by that extremity of the caterpillar's 

 skin which had not been split open. It has neither legs 

 nor arms, and yet it must free itself from this remaining 

 part of the skin, and reach the threads to which it is 

 to suspend itself. The supple and co7itractile segments of the 

 chrysalis serve for the limbs whieh are 7uanting to it. Between 

 two of thfse srgnients, as wi h a pair of pincers, the insect seizes a 

 portion of the folded skin, and -a th stick a firm hold that it is able 

 to support the whole of its body on it. It now curves the hinder 

 parts slightly, and draws its tail entirely out of the sheath in 

 which it was inclosed," &c. (The italics are mine.) How this can 

 be conceived possible, considering the utterly soft condition of 

 the newly-excluded pupa, and that the caterpillar skin is now 

 *' reduced to a packet so small that it covers only the end of the 

 tail of the chrysalis " {loc. cil. ), in which, moreover, there are 

 no longer any free segments, I cannot understand. On the 

 other hand, it is very tasy to show that the last and sufficient 

 bond of conneciion between the chrysalis and the old larv.i-skin 

 isrt membrane extending from the lining of the latter to the anterior 

 horns of the two lateral ridges bounding the anal area of thee h rysalis, 

 I have prepared several specimens showing this membrane still 

 intact, and should be happy to forward one or two, if required, 

 for inspection. I find it in all three species of butterfly men- 

 tioned above, and I believe it is to the persistence of it unbroken 

 that is owing the continued suspension of my chrysalides of 

 Anthocharis. I have tested its strength to sustain the weight of 

 the chrysalis, and the time during which it resists desiccation 

 and the writhings of the insect, the obvious object of which is, 

 not to get lid of the old caterpillar-skin, but to rupture this 

 membrane after the chrysalis has made good its tail-attachment 

 to the silk. J. A. OsB jrne 



Milford, Lettcrkenny 



The Satellites of Mars 



It is not necessary to have an enormous telescope in order to 

 see the outer satellite of Mars. 1 had a very satisfactory view of 

 it on September 15 at gh. 20m. with a nine-inch reflector, and 

 only lost it in the planet's glare at abjut loh. 50m. I would 

 have written to you on the subject earlier, but was not aware 

 that it was considered so extremely difficult an object until I read 

 the letters in your paper of the 27th ult. John Brett 



The Lizard, Cornwall, October 6 



Rate of Mound-Building 

 The papers announce that Mr. Layatd has obtained permis- 

 sion to renew excavations in the Mesopotamian Valley. Several 



other explorations will be in progress duiing the coining season 

 in countries where no trained labour can he obtained. I write 

 to beg the gentlemen having the work in charge to make some 

 accurate observations as to the amount of dirt which a man can 

 move in a day with rude implements, noting the distance as 

 well. A discussion has siirunj up concerning the time required 

 to build our Mississippi Valley mounds. The investigation of 

 which I speak will throw S3me light on the subject. 



Washington, D C, September 26 Otis T. Mason 



OU/i ASTRONOMICAL COLUMN 

 The Melbourne OESERV.\TORy.~The twelfth Report 

 of the Board of Visitors of this Obseivato-y, addressed 

 to the Governor of Victoria, with the Annual Report of 

 the Government Astronomer, is before us. It presents an 

 outline of the work accomplished between June 20, 1876, 

 and May 22, 1S77, and of the work in progress and in 

 prospective. With the great retlector, which is in charge 

 of Mr. Turner, the observation and drawing of Sir John 

 Herschel's figured nebulae has been continued. A finished 

 drawing of the Horse-shoe Nebula, M. 17, has bten 

 nude, together with drawings of fifty-seven of the 

 smaller nebulae. The publication of this work is in 

 progress ; out of ninety-three drawings which it is 

 intended to publish, sixty-one are already lithographed ; 

 they are represent? tions of the nebulie on a black 

 ground, and Mr. EUery states that they render the 

 telescopic appearance of the objects in a most ettective 

 and truthful style, and if the lithographic printers succeed 

 in obtaining the requisite number of copies as perfect as 

 the proof copies which were submitted to the Board of 

 Visitors, he considers that " the whole difliculty of 

 economically and satisfactorily reproducing these astro- 

 nomical drawings will be surmounted." The descriptive 

 letter-press will be ready by the time the lithography is 

 finished, and it is expected that before the next annual 

 inspection of the Observatory this first instalment of 

 results furnished by the great telescope will have been 

 distributed over the colonies and throughout Europe and 

 America. With the " South ecjuatorial " Mr. Ellery has 

 been engaged upon a woik of no small interest and 

 astronomical value, viz., the re-measurement of the 

 double-stars contained in Sir John Herschel's Cape 

 Catalogue, 1834-38, in which revision he is promised the 

 co-operation of I\Ir. Todd with the Adelaide refractor. 

 Mr. Ellery further mentions that he hoped to utilise the 

 present opposition of Mars, in connection with northern 

 observatories, for a determination of the solar parallax. 

 The transit-circle observations, which are regarded as the 

 main work of the establishment, are zealously continued. 

 The magnetic and meteorological work is upon the same 

 general plan as hitherto, but the former was likely, at the 

 date of the Report, to suffer some interruption from the 

 necessity of erecting a new magnetic-house. 



The Outer Satellite of Mars.— Though this object 

 will no doubt be growing fainter with the increasing dis- 

 tance of the planet from the earth, a few positions are 

 subjoined which have been deduced from elements fairly 

 representing measures made by Mr. Common, at Ealing, 

 to the end of September. The two or three days when 

 the moon will be near to Mars are omitted : — 

 At %h. 30/«. Greenwich Mean Time. 



Oct. II ... Pos. 



1. '2 ... ,, 

 .. 13 •■■ -, 



>, I4-- ,, 

 .. 15 ■■ ,, 

 ,, 16... „ 



At the times mentioned in Lord Rosse's letter (Nature, 

 vol. xvi. p. 457) the calculated places of the satellite were 

 as follows : — September 8, at iih. 45m., pos. 70°, dist. 83", 

 and September 15, at 1 th. jom., pos. 246", dist. 79". 

 The period of revolution given by measures between 



