488 SUMMARY OF CURRENT RESEARCHES RELATING TO 



seek to establish a series of homologies between the circumoral and 

 " lingual " regions in Bdellostoma and Petromyzon. They also maintain 

 that the so-called " tongue " of the Marsipobranchs is in reality the 

 detached lower jaw. Therefore the Marsipobranchs are true Gnatho- 

 stomes, forming a primitive group which probably sprang from the 

 common ancestry before the acquisition of paired appendages by the 

 vertebrate stock. 



Note on Phrynosoma.* — C. L. Edwards points out that Gadow is 

 mistaken in stating in ' The Cambridge Natural History ' that all the 

 species of Phrynosoma are viviparous. The fact is that the genus 

 contains viviparous species, e.g. Ph. doitglassii, but also oviparous species, 

 e.g. Ph. comutum of Texas, whose nest-building and ovulation Edwards 

 has described. 



Functional Inequality of the Kidneys.f — J. Albarran refers to 

 the general belief, which has some definite basis, that the kidneys func- 

 tion equally. His experiments on dogs and man do not confirm this. 

 He found that in the same time the two kidneys excreted different 

 quantities of urine and of dissimilar composition. The details of the 

 inequality are given, but it does not seem to us that the number of 

 cases and experiments was sufficient to warrant generalisation, though 

 the facts stated are undoubtedly interesting. 



Normal Presence of Arsenic in Animals. J — G. Bertrand has 

 applied his delicate methods for the detection of arsenic to a great variety 

 of animals from sponge to man. The metalloid seems to be present 

 in every case and in all sorts of tissues, and the author thinks that it 

 should be ranked like carbon, nitrogen, sulphur, or phosphorus as an 

 essential component of living matter. 



Arsenic in Eggs of Fowl.§ — G. Bertrand supports his view that 

 arsenic is a constant — perhaps physiologically necessary — component of 

 all cells by demonstrating that it occurs in appreciable quantity in all 

 parts of the hen's egg. The yolk has most, the white least, but even 

 the keratinoid shell-membrane s;ives the ieaction. 



S3* 



Formation of Black Pigment in Tumours of Horse. || — C. Gessard 

 refers to the recognised physical and chemical similarity of the melanin 

 of the eye, skin, &c. of mammals to the melanin of cuttlefish ink. He 

 has studied the melanic tumours of white horses, and finds that the 

 melanin is formed by the same biochemical process as that involved in 

 the production of cuttlefish ink. There are two agents involved, an 

 oxidising ferment and a chromogen. 



He finds that tyrosin is the chromogen whose oxidation by tyrosinase 

 determines the formation of black pigment in many normal and ab- 

 normal products in the animal series. One may say indeed that the 

 colour of the negro is due to the same reaction as that which occurs in 

 making the ink of the cuttlefish or the black of certain fungi. 



* Science, xvii. (1903) pp. 826-7. 



t Comptes Rendus, cxxxvi. (1903) pp. 1207-10. 



j Ann. Inst. Pasteur, xyii. (1903) pp. 1-10. 



§ Comptes Rendus, cxxxvi. (1903) pp. 1083-5. j Tom. cit., pp. 1086-8. 



