ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 241 



Mexican Species of Argas.* — M. P. Megnin gives an account of 

 three Mexican species of this spider: Argas turicata, A. talaje, A. meg' 

 nini; the first of these does not limit its attacks to pigs, but affects also 

 the human subject, where it is found in the auditory meatus, and 

 sometimes produces severe illness. A. talaje is likewise very irritating, 

 and both species seem to have a secretion analogous to that of the 

 Tarantula. A. megnini appears to be a far less troublesome parasite. 



€, Crustacea. 



Blood of Crustacea-t — Dr. W. D. Halliburton's observations on 

 the blood of Crustacea have been made on the more common decapods ; 

 it was obtained by making cuts in the soft ventral integuments or in 

 the claw ; from a large lobster nearly half a pint can ordinarily be 

 obtained. It is at first nearly colourless, or of a reddish colour, and 

 is milky from the presence of numerous amoeboid corpuscles ; but this 

 soon disappears owing to the almost instantaneous occurrence of 

 coagulation. After a few minutes' contact with the oxygen of 

 the air it gets an indigo-blue tinge, due to the oxygenation of a 

 proteid body which is dissolved in the plasma, and has been called 

 hgemocyanin by Fredericq. The specific gravity varies between 1025 

 and 1030, and the reaction is always faintly alkaline. The author 

 describes in detail the phenomena of spontaneous coagulation, and 

 finds that it is in nearly all respects similar to that of vertebrate 

 blood. 



The proteids of the blood-plasma are the already mentioned 

 hsemocyanin, and fibrinogen ; the serum contains only the former, 

 which resembles serum globulin in certain points, but differs from it 

 in containing copper, in coagulating at 68° C. or seven degrees lower ; 

 it is more difficult of precipitation from its solutions by saturation 

 with salts, and it is completely precipitated and coagulated by strong 

 acetic acid. 



Crustaceous fibrinogen resembles generally that of vertebrates, 

 but differs by coagulating at 65° C. or 9° higher, and in not being 

 precipitated by sodium chloride completely, unless the solution be 

 saturated with that salt. 



The colouring matters of the blood are the blue hsemocyanin, and 

 a red tetronerythrin ; the former is the oxygen carrier. Though 

 the author thinks that the latter pigment may have respiratory 

 functions, he does not base this view on the arguments advanced by 

 Merejkowski. 



Dealing with the comparative aspects of crustacean blood. Dr. 

 Halliburton reminds us that in some there is hiemoglobin, and that 

 haemocyanin is found in Cephalopoda, Gastropods, and Arachnids. 

 In an appendix he gives a useful list of the animals in which these 

 two colouring matters, chlorocruorin, haemerythrin, chlorophyll, and 

 tetronerythrin have been found. 



* Journ. Anat. et Physiol. (Robin), xxi. (1885) pp. 460-75 (2 pis.), 

 t Journ. of Physiol., vi. (1885) pp. 300-35 (1 pi.). 

 Ser. 2.— Vol. VI. R 



