1910.] Blood in Veo'tehrates and Invertehrates. 615 



water forms, and it is not improbable that the Ganoid ancestor of the 

 Teleosts was a fresh-water form or one which, like the sturgeon, occasionally 

 occurred in brackish watei'. 



The ratios of the sodium, potassium, calcium, and magnesium in the serum 

 of these marine fishes are not on the whole very different and they approach 

 those in the mammal. In the cod the potassium ratio (9'506) is high, and 

 this may be due to a slight laking of the red corpuscles, whicli are rich in 

 salts of that element. The ratio value for potassium in the pollock (4-33) is 

 less than half of that in the cod, and it closely approximates that in the 

 dogfish (4' 61). The ratios in the dogfish and pollock are almost the same, and 

 the difference is most marked only in the magnesium, which is more 

 abundant in the former. 



This excess in magnesiiim is apparently one of the results of the action of 

 the sea water on the blood of the dogfish for all the tune which has elapsed 

 since the Vertebrate type arose, for the Elasmobranchs have, as already 

 stated, been marine since their origin, which is, at the latest, Devonian and, 

 if the Ostracoderms are Protoelasmobranch, probably early Silurian. The 

 ratio for magnesium in the dogfish is, however, only a little more than one- 

 fifth of that found in Limulus, which has been also since its origin in the 

 Cambrian a marine form. 



That the Teleosts have been oceanic for a much shorter time than the 

 Elasmobranchs is shown in the osmotic pressure of their blood as measured by 

 the A. In Elasmobranchs this varies somewhat with the species and the 

 habitat, but from the determinations of Bottazzi,* Eodierf and others it has 

 been found to lie between the values —2-03° C. and —2-44° C, while the 

 sea water of the habitat of the animals, as a rule, gave a slightly lower A than 

 the serum. In the dogfish the A was — 2'03o° C, of which the salts 

 contributed —1-0737°. In the Teleosts it is always much less, rarely does it 

 exceed —l°t and it ordinarily ranges between — 0"466° in Tinea v^dgaris and 

 — 0 838° in Gadus virem.%^ In Gadus morrhua, according to Dekhuyzen, the 

 A varied according to the locality from which the fish was taken and the 

 minimum and maximum values were — 0'644° and — 0'811°. In the blool of 

 Gadus callarias, as shown above, the salts gave a A of — 0 71° C, while that 



* ' Arch. ital. de Biol.,' 1897, vol. 28, p. 61. 



t ' Travaux des Lab. de la Soc. Scientif. et Station Zool. d'Arcachon,' 1899, p. 103. 

 Reference in Hamburger, ' Osmotischer Druck und louenlehre,' vol. 1, p. 465. 



I Bottazzi found the A in two specimens of Char ax puntazzo to be — 1'04° and — 1*035 °, 

 and in a specimen of Cerna gigas it ■<ki\s, — 1"035°. Dekhuyzen questions these results as 

 thej' were obtained with a cooling bath of —12° C. 



§ M. C. Dekhuyzen, ' Kon. Akad. van Wetensch.,' Amsterdam, vol. 8, p. 537, 1905. 



