January 12, 191 1] 



NATURE 



351 



nude by M. F. Sy at the Algiers Observatory. Positions 

 ••_• given for the period April lo to July lo, and the 

 irious phenomena of the head and the tail are briefly 

 : scribed. Observations of Venus and the comet, as sug- 

 , sted by Prof. Birkeland, were made, under adverse con- 

 it ions, on May 2, but no special phenomena were re- 

 Kirked. Similar duplications of the nucleus to those re- 

 irded at Johannesburg were observed on May 3, 8, and 

 iter dates, but only a single nucleus was seen on May 5. 

 \ notable recrudescence of brightness apparently took 

 lace on July 9, as compared with July 5 when a nebu- 

 sity, 1' in diameter, and no nucleus were seen. Refer- 

 loes to these alternating duplications of the nucleus are 

 lude in the December (1910) number of the Bulletin de 

 1 Societe astronomiqiie de France, where MM. Millochau, 

 Borrelly and others describe their observations. M. 

 J amain finds that the successive appearances are best 

 explained by the supposition that the nucleus of the comet 

 had a rotatory motion, with a period of about 21-5 hours. 



In No. 4461 of the Astronomische Nachrichten Dr. J. 

 Mascart reproduces three excellent photographs, and three 

 drawings of the head, taken at his special observing station 

 at Teneriffe during May and .April respectively ; the com- 

 plicated structure of the head on April 16 and 18 is especi- 

 allv remarkable. But Dr. Mascart deals chieflv with the 



^4i 



OS THE ORIGIN OF SLAIEKY AND 

 PARASITISM IN ANTS. 

 T'W'O interesting papers on the origin of slavery and 

 ■■■ parasitism in ants, by Henri Pi^ron, Maitre de Con- 

 ferences a I'Ecole pratique des Hautes-Etudes, have 

 appeared recently in the Revue generale des Sciences 

 (September 15 and 30, 1910), and the main points are sum- 

 marised below. The papers are conveniently divided into 

 sections, and are rendered more valuable by full references 

 being given for all the statements referred to. 



I. Females : Foundation of Colonies. 

 (i) Foundation of a New Nest by a Fertilised Female. — 

 After the marriage-flight of ants, the males and females 

 fall to the ground, when the males die, and those of the 

 females which escape the numerous dangers to which they 

 are exposed taken refuge in crevices in the ground, where 

 they lay their eggs. For a month or more the female 

 appears to subsist largely by the absorption of the alary 

 muscles, now no longer required ; but in some cases, as 

 in Atta sexdens, the female carries with her a supply of 

 the mycelium of an edible fungus,, on which she and her 

 progeny afterwards subsist. . The earliest hatched workers 

 in nests founded by a single female share her privations, 

 being much smaller than those hatched later. In some 



Fig. 2.— Changes in the Head of Hallty'a Comet, as oi served at the Transvaal Observatory-. 



conditions of observation on a mountain site, and strongly 

 emphasises the advantages which accrue from the establish- 

 ment of an astronomical observatory in a clear atmosphere 

 and at a high altitude, yet more or less readily accessible. 

 Finally, he suggests the necessity for establishing an 

 important and permanent international observatorv' on 

 Mount Guajara, w'here he was stationed. Dr. Mascart 

 gives more details, and discusses such matters as the 

 zodiacal light, &c., in an article which appears in the 

 December C1910) issue of the Rivista di Astronomia, Turin 

 (vol. iv.. No. 12, p. 585). 



\ note in the December (1910) number of the Observa- 

 tory (No. 429) suggests that, as the comet has now 

 sufficiently emerged from the sun's rays, a few more 

 observations may be secured, even in European latitudes, 

 before it finally disappears until August, 1985. An 

 ephemeris for Greenwich midnight, and extending to the 

 end of March, is given ; as the declination is about 18° 

 south, those observatories situated in the southern hemi- 

 sphere will enjoy better conditions. At present the comet 

 is apparently situated in the constellation Corvus, and is 

 travelling slowly in a south-westerly direction ; its position 

 for December 31, 1910, is R..A.=:iih. 53-4m., dec.= 

 18 12-7' south, but after January 11 it will again com- 

 mence to travel northwards. 



NO. 2150, VOL. 85] 



cases a portion of the eggs are sacrificed for the nourish- 

 ment of the female and the newly hatched larvae, and are 

 also used by .4. sexdens as a hot-bed for the fungus. 

 Some of the species of ants in which nests are founded by 

 a single female are among the oldest in existence, going 

 back, almost unchanged, to Tertiary times. 



(2) Foundation of a New Colony in a Pre-existent Nest. 

 — Female ants will sometimes take up their abode, and 

 rear a fresh colony in the deserted nests of other species, 

 or even, on more or less friendly terms, establish a 

 colony of their own in inhabited nests of other species. 

 On the other hand, ants of the genus Solenopsis, &c., 

 usually form nests in small galleries round and com- 

 municating with the nests of larger species, which they 

 plunder at will, without the larger ants being able to 

 pursue them into their narrow fastnesses. 



(3) Foundation of a New Nest with the Aid of Workers 

 of the same Species. — The females of some ants are unable 

 to form a new colony without the aid of workers, and if 

 they fall to the ground near their own nest, or one of the 

 same species, they may return to the nest, or may be joined 

 by a colony of workers, and thus assisted to establish a 

 new one. 



(4) Foundation of a New Colony with the Aid of 

 Workers of another Species. — .Although ants usually 



