1884.] 



MICROSCOPECA.L JOURNAL. 



17 



periment and observation have served 

 to strengtlien it in several cases. Per- 

 haps the hitest observer in this direc- 

 tion is Mr. F. Dahl, who has convinced 

 himself that there are auditory hairs 

 on the arachnida. These hairs are of 

 tv^^o kinds, placed on the legs and 

 palps ; one is short, of uniform thick- 

 ness, and fringed at the apex ; the other 

 longer and projecting outward more 

 than the ordinary hairs. The former 

 is very mobile, implanted in a cup- 

 shaped depression, and connected 

 with a nerve at the base. 



Under the microscope the hairs 

 have been observed to. vibrate during 

 the sounding of a note. It is sup- 

 posed that the different lengths of the 

 hairs adapts them to receiving differ- 

 ent notes. The author classifies the 

 spiders of Germany in accordance 

 with the arrangement of the hairs as 

 follows : — 



1. Epeiridce and Theridiidce. — 

 Tibia with two rows of auditory 

 hairs ; metatarsus with a single hair ; 

 tarsus with a depressive, but no pro- 

 jecting hair. 



2. Salt i dee ^ Thomsidce ., Lycosidce. 

 — Tibia, metatarsus, and tarsus, all 

 with two rows of hairs. 



Researches on Chlorophyll. 

 — The coloring matter of chlorophyll 

 has been studied by many persons 

 with a view to determine the modifi- 

 cations to which it is subjected, and 

 also its functions, in the physiological 

 processes of the plant. So many 

 modifications have been found, or so 

 many difierent coloring principles 

 have been distinguished in it, that the 

 subject is very confusing. The re- 

 searches of Pringsheim upon the ef- 

 fects of light upon chlorophyll in the 

 plant, and the production of starch, 

 are of great interest, and have already 

 been referred to in these columns. 



A. Tschirch has studied the color- 

 ing matter of chlorophyll, and some 

 of his experiments may be readily re- 

 peated by other observers with great 

 interest. He obtains from an alco- 

 holic solution of the green coloring 



matter of plants a substance which 

 he names chlorophyllan, and which 

 appears to be the hypochlorin of 

 Pringsheim. Chlorophyllan is the 

 first product of oxidation of the chlo- 

 rophyll pigment in the presence of 

 acids, and as vegetable acids are al- 

 ways present in alcoholic solutions of 

 chlorophyll, it is always formed in 

 such solutions. It can be obtained in 

 several ways. Perhaps the simplest 

 method is to evaporate an alcoholic 

 solution of chlorophyll, wash the resi- 

 due with water, then dissolve in ether, 

 and allow the chlorophyllan to crys- 

 tallize out of the etherial solution. 



Chlorophyllan is insoluble in water, 

 soluble in alcohol, ether, and benzine, 

 giving brownish-green solutions. It 

 may be reduced by powdered zinc to 

 a green substance, probably identical 

 with chlorophyll. 



The yellow substances of chloro- 

 phyll can be obtained from a solution 

 of the latter by heating the solution 

 with baryta-water, which produces a 

 precipitate, from which alcohol will 

 dissolve the yellow product or xan- 

 throphyll. 



To obtain pure chlorophyll the 

 chlorophyllan may be reduced by 

 means of zinc, as already stated, or 

 by treating a concentrated alcoholic 

 solution of the green matter of plants 

 with baric chloride, in which the 

 pure coloring matter is insoluble. 



Splrogyra^ or any of the green algje 

 which abound in pools and streams, 

 afford a good source of chlorophyll 

 for experiment. They should be cut 

 up and digested in alcohol. 



CORRESPONDENCE. 



The Measurement of Blood-Corpuscles. 



To the Editor. — I hoped to give, in 

 the January Journal, some further remarks 

 on this subject and some interesting re- 

 sults, but lack of time has prevented. I 

 shall try to do so next month, but in the 

 meantime I think it is well to notice briefly 

 some misinterpretations of my article in 

 the December number. 



First : I do not say the average size of 

 human blood discs is ^f^nj, but that it is 



