SCIENCE- GOSSIP. 



T 5i 



MICROSCOPY 



;!(* 



CONDUCTED BY P. Kl-II ISLINGTON SCALES, F.R.M.S. 



Mosquitoes and Malaria. — Professor B. 

 Grassi discusses the observations of . Koch in a 

 recent paper published in Italy. He dors riot con- 

 sider they have made any contribution to the 

 aetiology of human malaria.. It is also indicated 

 that Ross's discoveries are suggested by, and are 

 confirmatory of, Grassi's previous results. 



Role op Insects, etc., as Carriers op 

 Disease. — For the following summaries we are 

 indebted to the Journal of the R.M.S. Dr. G. H. 

 F. Nuttall. in the Johns Hopkins Hospital Report 

 VIII., 1899 (see also Lancet, September 16th, 1899), 

 makes a timely and valuable contribution to the 

 literature of animal and vegetable parasites, and 

 their definitive and intermediary hosts. This 

 occurs in a critical and historical study of the part 

 played by insects, arachnids, and myriopods as 

 carriers of bacterial and parasitic diseases of man 

 and other animals. Among the more important 

 and interesting features of the essay may be men- 

 tioned the evidence adduced to establish the con- 

 nection between flies and the spread of cholera, 

 typhoid, and plague, the association of Texas or 

 tick fever with Ixodes bovis, of tsetse-fly disease 

 with Qlossinia morsitans and its recent visit to an 

 infected animal, the subject of filariosis, and the 

 mosquito-malaria theory'. The bibliographical ap- 

 pendix is extensive. 



Regeneration in Earthworms. — A. P. Hazen 

 has made some interesting experiments. It has 

 been shown by Spallanzani, Morgan, and Hescheler 

 that a short piece cut from the anterior end of an 

 earthworm dies without regenerating the posterior 

 end, although such a piece often lives for several 

 weeks, or even months. It was not known, how- 

 ever, whether, if such pieces could be kept alive 

 for a longer time, they would regenerate ; or 

 whether, if regeneration did occur, a head or a tail 

 would develop. By grafting in a reversed direc- 

 tion the small anterior end of one worm upon a 

 large posterior piece of another worm, the small 

 piece can be kept alive for a much longer time. 

 The results showed that a head may regenerate 

 from the posterior end of the seventh segment if it 

 is kept alive for some months by grafting. It 

 seems, comparing this with other experiments, that 

 the part of the body of the normal worm from 

 which the segments are taken determines what 

 will be regenerated, rather than the direction in 

 which regeneration takes place. 



Story op Artemja retold.— In 1875 W. 

 Sehmankewitsch published in the " Zeitschrift 

 fur wissenschaftliche Zoologie " a famous paper 

 giving an account of his observations on the brine 

 shrimp, Artemiq salina, from the Bay of Odessa. 

 He stated that by altering the water he could 

 transform A. salina into another species, A. miiJil- 

 haiisenii; and, mure than this, that by the addition 

 of fresh water to the habitat in which .1 salina 



lived he could induce a resemblance to tie' genus 



Jlranrliijiiis almost amounting in identity. Both 

 results have been repeatedly criticised ; tin- second 

 has been proved inaccurate, and much doubt has 

 arisen in regard to the first. The mosl thorough- 

 going criticism, however, has been that of \v. p. 

 Ai nk in, published in Russian in L898, but now made 

 available fco the unlearned iii thai language by a 

 summary by N. von Adelung in German. Ainkin 

 points out, that tin' various species of Artemia 

 which have been described <\n not rest on a 

 satisfactory basis — not that they are alone in 

 that — and that some of them are merely cripple- 

 modifications of A. salina, induced \,\ 

 alterations in the salinity of the water. His ex- 

 periments showed that if the degree of con- 

 centration was slowly and gradually increased, no 

 structural changes of moment ensued. Some slight 

 changes were, indeed, observed ; but they were only 

 " modifications," not transmissible to the progeny, 

 and disappearing when normal conditions were 

 restored. Moreover, these slightly different indivi- 

 duals were sometimes found together in the same 

 water. It is to be hoped that no one will imagine 

 that the question is closed, but that we shall have 

 more experiments on Artemia; in the meantime, 

 however, Ainkin's four general conclusions will be 

 read with interest. The representatives of the 

 genus Artemia show a marked tendency to change, 

 as regards almost all the organs of their body. 

 The form-changes depend mainly on the physico- 

 chemical character of the medium. The changes 

 in individuals which live in salt solutions subject 

 to constant dilution with fresh water do not indi- 

 cate any transformation of Artemia into Branchi- 

 pvs ; even those in the least salt solutions retain 

 unchanged the characteristics of their genus, 

 especially in the male sex. The concentration of 

 the salt solution has certainly an influence on the 

 length of the post-abdomen, for in dense solutions 

 those with long post-abdomens predominate, in 

 weak solutions those with short post-abdomens. 



Mechanical Stage for Diagnostic Micro- 

 scope. — Mr. Charles Baker has added to his 

 ■' Diagnostic " microscope, noticed by us in this 

 journal, vol. vi. p. 182, a detachable mechanical 

 stage by which the whole of a 1^ inch x | inch 

 cover-glass can be examined. We illustrate this 

 FIB 



stage herewith. The lower plate fits on to the 

 stage of the microscope, and has a vertical move- 

 ment thereon by means of runners, aided by a 

 screw at the top, which, however, gives movement 

 in one direction only. The screw at the -id.' gives 

 horizontal movement for § inch both backwards 

 ami forwards, and there is a sliding top plate 

 which can be pushed over so as to increase the 

 travel for a further | of an inch. The stage is thus 

 well designed tor systematic examinations over a 

 large field. The price is £2 5s. 



