1910.] Blood in Vertebrates and Invertebrates. 



605. 



inorganic composition of the blood of the horseshoe cxah, Liriudus polyphemuS; 

 and their results are in agreement only in the most general way. While the- 

 discrepancies are in some cases at least extraordinarily great, Genth's results 

 even as regards the composition of the blood of forms from two different, 

 points on Chesapeake Bay are quite unlike, and the question is raised 

 whether the variations are due to imperfect methods of analysis or to actual 

 differences in composition. That his methods did not give exact results may 

 be gathered from the fact that the percentages of potassium in the samples 

 of blood from the two different sources were widely different, the element 

 appearing to be twice as abundant relatively in one case as in the other. 

 This is to a certain extent intelligible, for the methods of estimating potassiumi 

 employed 60 years ago were much less exact than they are now, but even 

 a defective method ought under like conditions to give uniform results. 



The differences also between the results of McGuigan, on the one hand,, 

 and those of Gotch and Laws on the other, would, if accepted, make it 

 impossible to regard the blood in Limuhis as uniform either relatively or 

 absolutely in its inorganic composition. That would entail the further 

 conclusion that in Limulus, after a life in the sea almost co-extensive with 

 geological history, there is a tendency to wide variation in the inorganic 

 composition of the blood, irrespective of the changes in the concentration of 

 the salinity of the sea water of its habitat. If that conclusion were correct 

 it would indeed be difficult to understand how fixed relations in the inorganic 

 composition of body fluids ever could arise, and the primal causation of 

 such fixed relations in, for instance, mammals would be an enigma. 



So far, therefore, the results of analyses hitherto made on the blood of 

 Invertebrates leave the question of the origin of the fixed proportions of 

 tlie inorganic elements in the blood of the higher Vertebrates still in? 

 doubt. 



In order, therefore, to dispose of the question of the origin of these fixed 

 proportions it was necessary to analyse the blood of representatives of the 

 lower classes of the Vertebrates and of Invertebrate types with a closed 

 circulation. This involved the collecting of quantities of blood plasma from 

 a number of forms, many of which are not accessible ordinarily and, in 

 consequence, the determination of the problem has been delayed far beyond 

 the limit originally set in the writer's plans. 



Within the last two years he succeeded in obtaining a quantity of material 

 which has enabled him to undertake a partial investigation of the question. 

 Through the kindness of the Director of the Woods Holl Biological Station 

 he received a large quantity of the blood of the horseshoe crab, Limulus: 

 polyphemus. During his visit to the Canadian Marine Biological Station at- 



