NA TURE 



[December 31, 1908 



tropical 



THE VACATIONS OF A NATURALIST. 



THOSE who have read " In Northern Spain," 

 published some years ago, will welcome another 

 book of travel by the same author. In the years 1902 

 and 1904 he spent the long vacation in the south of 

 Mexico in search of zoological specimens, and the 

 present volume not only gives us an entertaining 

 account of the experiences of himself and his wife 

 in localities which are still but little known, but it is a 

 collection of scientific observations and speculations of 

 considerable value, in which, though zoology naturally 

 takes the first place, other branches of research are 

 by no means neglected. He spent a considerable 

 portion of his time in the tierra calientc. the hot 

 tropical lowlands, at a season — from June to .Septem- 

 ber — when vegetable and animal life exhibits the 

 greatest luxuriance and activity. It is, however, a 

 period of excessive heat, and in most places heavy 

 rainfall, so that readers of the book will obtain an 

 undulv unfavourable impression of life 

 America. .At other times he was at 

 work on the invigorating table-land of 

 Mexico or the slopes of its lofty 

 volcanoes. 



Evervwhcre he was successful in nh- 

 taining specimen.s of new or ran- 

 forms of life, and to those who know 

 the diflficulties of carrying through a 

 programme where the bridle-path and 

 mule-train are the only means of trans- 

 port, the amount that he was able to 

 .accomplish in the limited time at his 

 disposal will seem marvellous. 



The book commences with a descrip- 

 tion of the environs of the capital, and 

 gives an interesting account of Lake 

 Xochimilco, famous for its floating 

 gardens and the axolotl thai inhabits 

 its waters, the questions which arise in 

 connection with the life-history of the 

 latter being discussed in some detail. 



The travellers spent some time on 

 Citlaltepetl, el Volcan de Orizaba. 

 where the author was struck by the 

 abrupt character of the upper limits of 

 ))lants on the mountain-side. " Ti7- 

 laiidsia tricolor disappears quite sud- 

 denly from the southern slopes at aboui 

 9600 feet ; the last specimens are ju--t 

 as large and flourishing as those lower T)ie ■ Chinampas 

 down, whilst the conifers upon which 

 they grow, continue without the 

 slightest change. The Piiius liophylhi and the Abies 

 n'lisiosa cease at their upper level as v(>rv big 



n ■ 1 



trees. ' 



The author obtained five species of the land-newt, 

 Spelerpes, one of which, .S. varicgalus, was ultimately ', 

 found to extend from an altitude of 9000 feet to the 

 tropical lowlands. He states that " a boxful of 

 .S. variegatiis that he collected in a day's excursion 

 in a tropical region south of Cordoba lived verv well 

 on Citl.-dteiJell in spite of the low temperature, but 

 those brought from that mounl;iin died within a few 

 davs when taken into the tropics ; and he considers 

 this to corroborate " the fact that most creatures can 

 endure a temporary change into cooler surroundings, 

 even though they may not flourish under it, while the 

 reverse of such conditions, prostrates and kills them." 

 It is, however, doubtful whether this is true of 



' " Through Siu'hern Mexico. Being an Account of the Travels of a 

 Naturalist." By Hans Gadow, F.R.S, Pp xvi + sz?. (London : Witherby 

 and Co., 1508.) Pricei8j.net. 



NO. 2044, VOL. 79] 



warm-blooded .-inimals. On the other hand, he con- 

 tends that there are many more species of anim.il- 

 and plants, which have their " probable centre of 

 origin in temperate climates, and now extend inlu 

 the tropics and yet remain apparently unaltered, than 

 there are hot country species which have spread inln 

 cool climates." 



From Orizaba the travellers passed to the low-lying 

 forests of the Rio Tonto, on the northern side of the 

 Isthmus of Tehuantepec, where a goods van shunted 

 on to a siding formed their headquarters. The 

 author's description of a tropical forest is so true- to 

 nature that part of it may be quoted here : — " It does 

 not begin gradually. On its outskirts it is fringed 

 by an impenetrable wall of luxuriant herbage, shrubs 

 and creepers. ... It can be entered only by hacking 

 and slashing a path through the tangled growth, 

 which closes up again witliin a few weeks, e.xce])t 

 where traflic mav have produced a narrow, meander- 

 ing track, from which it is impossible to deviate 

 either to right or left. Once inside, we are in a 



lardens of Lake Xochimilo 



"Thriigh Southern 



gloomy. Stuffy forest consisting of tall, straight trees, 

 which branch out at a great height above us, there 

 interlacing and forming a dense canopy of green 

 through which passes little or no sunlight. The 

 ab.sence of direct light effectively prevents the growth 

 of underwood, and there are no green, luxuriant 

 plants, no flowers or grass. The ground is brown 

 and black, covered with many inches of rotting leaves 

 and twigs, all turning into a steaming mould. From 

 our point of view below the canopy the leaves, 

 branches, and even bright-coloured birds look black, 

 and this is still more the case where, by contrast, 

 such objects ate seen through a rift in the canop.v 

 against the glaring sky." 



Prof. Gadow describes in detail the adaptation of 

 different groups of animals to forest life, and lays stress 

 on the fact that, given the same conditions, the out- 

 ward characters of different forms become almost iden- 

 tical. Si^eaking of the arboreal Anura, he tells us that 

 " the forests have succeeded so well th.-it it is, for in- 



