54 



KNOWLEDGE. 



[March 1, 1901. 



uoithern or Ai-ctic regions. Nevertheless it reappears on 

 the Atlantic sea-board of North America, and American 

 zoologists have made its life-history the subject of de- 

 tailed and careful study. Like all the Spring-tails and 

 Bristle-tails, Anurida passes through no transformation 

 after hatching; the tiny insect leaves the og^ in a form 

 closely like that of its parent. But the deve'lopmeut of 

 Anurida within the egg forms the theme of several 

 valuable embryological researches+I by Profs. Rvder and 

 Wheeler, Miss Claypole, and Dr. J. W. Folsoni. With 

 a notice of one or two important points brought out by 

 these investigators our study of marine Spring-tails may 

 fitly close. 



The earliest study of the growth of Anurida (Prof. 

 Ryder's) established the interesting fact that a rudiment 

 of the lost spring exists in tlie embryo, and a vestige of 

 the organ is still present when the insect is hatched. 

 We thus have sure evidence that the absence of the 

 spring in the adult is due to degeneration, as there can 

 be no doubt that, in such a matter as this, the life-history 

 of the individual represents approximately that of file 

 race. 



Ill our account of the Bristle-Tail. MucliiUs maritimn. 

 the possible near relationship of primitive insects to 

 primitive crustaceans was discussed. Every one knows, 

 however, that while most crustaceans have two pairs of 

 feelers on the head, insects have only one pair. But 

 there are several insects in whose embi-yos a vestigial 

 pair of appendages between the feelers and the mandiijlBS 

 have been observed. Anurida is one of these. At a 

 very early stage in the progress of growth, a pair of tiny 

 processes (Fig. 6, A, tc) bud out from the germ band 

 behind the feelers. There can be no reasonable doubt 

 that these represent a second pair of feelers, lost by all 



Fio. 6. — A. — Earl.y embrju of Aiiunda. (.Vfter Wheeler.) 

 ?, upper lip; ant, feelers; <e, vestigial appendage.s ; md, 

 mandibles; )n.r', mx-, first anil seeond maxilla:-; jii, inst. 

 tnlt, the three pairs of legs. B.— Head region of later embryo. 

 (After Folsom.) ?«.r/, rudiments of maxilliilie; other lettering 

 as in A. Highly magnified. 



living insects, but retained by the great majority of 

 crustaceans. 



t+ •)■ .\. K.vder. ■■ Tlie Development ot \1111rid4 luaritima." 

 Amer. Sal., Vol. XX., 1886. pp. 299-302, pi. X\'. 



W. M. Wheeler. '' A Contribution to Insect EmbiTologv." Journ 

 Morph., Vol. VIII., 1893, pp. 1-160, pis. I.-VI. 



A. M. Claypole. " The Embryology and Oogenesis of Anurida 

 maritima." Journ. Morph., Vol. XIV., 189H im 21!t-300 

 pis. XX. X\V. ' 



J. W. Folsom. "Tlie Development of the .Mouth Parts nf ,\ruu'ida." 

 Bull. Mils. Comp. Zool. Harvard. Vol. XXXVl., 19ou, pp 87-158 

 pU. l.-VIIl. i-r , 



An important structural point wherein Spring-tails 

 agree with Bristle-tails is the possession of the paired 

 organs at the base of the tongue — the " maxillulae " {see 

 p, 21, anie), believed by Dr, Hansen to represent the 

 first maxillaB of crustaceans. Now Dr. Folsom, the most 

 recent student of the gi-owth of Anurida maritima, has 

 traced the development of these organs in great detail. 

 He finds that they arise from a pair of rudiments 

 (Fig. 6, B, mxl) situated between the mandibles, al- 

 together similar to the rudiments of the other paired 

 limbs, and having a nerve-centre (ganglion) and a division 

 of the primitive body cavity (coelom) associated with 

 them. There seems, therefore, no doubt that a primitive 

 segment with paired limbs, between the mandibles and 

 maxillae, is indicated by the method of growth as well as 

 by the developed structures ; and furtlier support is thus 

 accorded to the relationship between early insects and 

 crustaceans to which reference has already been made. 



Thus we see that minute details in- the obscure life- 

 history of these humble insects of the sea-shore — details 

 only to be learnt by long and careful research — help us 

 to trace the history and relationships of some of the 

 largest and most important classes of the Animal King- 

 dom. 



RAINFALL IN SOUTH AFRICA. 



By Arthur H. Bell. 



The presence of so many of qui- troops in South Africa, 

 as well as so many others of oui' countrymen who may 

 be contemplating a prolonged sojourn there, renders the 

 subject of the climate in which they ar-e living an 

 important one; and of all the elements likely to have-an 

 effect on the development and future prospects of the 

 country none will be so fai' reaching as rainfall. Indeed 

 differences in climate, after all, px"ove to be barriers 

 which separate different races of men from one another, 

 and questions of temperature may, in the long run. be 

 found to regulate the extent to which any given class 

 of men may advance into untried regions of the earth. 

 At times it seems to be assumed that the Anglo-Saxon 

 race niay with impunity settle down in any quarter of 

 the globe whatsosver, and may do so without experiencing 

 any phj-siological inconvenience from submitting bodily 

 functions and organisms to a climate to which they are 

 unsuitsd. A hot inoist climate mav, however, prove more 

 effective in limiting the peregrina-tions of adventurous 

 races than the artifices of diplomacy or a complete 

 equipment of modern armaments. This possibility 

 renders the vagaries of climates in distant parts of the 

 globe of permanent interest, and, as stated above, an 

 important matter for consideration at the present 

 moment is as to whether past meteorological records 

 throw any light on the future prospects as regards 

 rainfall in South Africa. To those who daily experience 

 the comfort of having four brick walls between the 

 wind and their nobility the changes in the weather 

 are of comparatively little moment ; but in opening up 

 a new country there is much camping out to be done, 

 and those whose lot it is to sleep under canvas are likely 

 to find the question of rainfall an important one. For- 

 tunately a veiy excellent series of rainfall observations 

 is available for elucidating the subject, for such obser- 

 vations have been made in South Africa at a very lai-ge 

 number of stations and during a large number of years, 

 the stations being distributed over a wide ai'ea of 



