36 ARKIV FÖR ZOOLOGI. BAND 2. NIO 8. 



It may be useful to say some words on the chief diffe- 

 rences between more than half-grown but still immature spe- 

 cimens and the adults. In such immature specimens the legs 

 are proportionatejy shorter and thicker than in adults of the 

 same sex; in the first pair of legs tibia is, at least generally, 

 conspicuously shorter in proportion to the foot (consisting of 

 metatarsus and tarsus), the foot itself is always less slender, 

 with the metatarsus proportionately shorter and the terminal 

 tarsal joint proportionately longer than in the adults; fem ur 

 of fourth pair of legs is deeper in proportion to its length. 

 Flagellum of immature females is proportionately thicker, with 

 the articulations less conspicuous or scarcely visible or even 

 wanting ; flagellum in immature males diff ers very much from 

 that in the adults, but it is yet somewhat thickened and 

 unjointed. The descriptions of species of which both adult and 

 immature specimens have been examined, are founded only 

 on the adults; the immature specimens are dealt with in a 

 special paragraph: »Differences according to Age.» 



Geographical Distrilbutioii. — Of the fifteen species descri- 

 bed liere two have been secured in Venezuela, two in the is- 

 land of Martinique, one is from Sierra Leone (west-coast of 

 Africa), one from the islands of Seychelles (western part of 

 the Indian Ocean), two are from Ceylon, five from Lower 

 India with Malacca — viz. two from Burma, one from Siam, 

 two from Singapore — one is from Luzon (Philippine islands), 

 and one from New Guinea and New Britannia. Cook mentioned 

 one species from Liberia and established one from California. 

 With exception of the last-named country all the other loca- 

 lities are found in the tropical region: they are spread över 

 the greater part of its length all round the globe. But I am 

 quite sure that even af ter the publication of this paper we 

 do not know one fifth of the species of Tartarides. In three 

 papers published 1901 — 1903 I have shown that our knowledge 

 of the forms of three orders of small terrestrial Arthropoda, 

 viz. Palpigradi, Pauropoda and Symphyla, is exceedingly poor; 

 I increased the number of species from respectively two and 

 a half to six times (Palpigradi from two to six, Pauropoda 

 from fourteen to thirty-six, Symphyla from four to twenty- 

 four species) and stated, that still we know only a small portion 

 of the species existing; in a book by Dr. W. Sörensen and 

 myself published half a year ago the number of species of a 



