ON THE BRITISH ANNELIDA. 17$ 



Mr. Wharton Jones describes and figures the blood-corpuscles of the Earth- 

 worm and the Leech, and thus defines the mode in which he obtained the 

 specimens submitted to examination : — 



" The blood was most readily obtained for examination from the abdominal 

 vessel, but in abstracting it, care was required to guard against its becoming 

 mixed with the secretion poured out from the skin in great abundance when 

 the animal is wounded," p. 94: Mr. Jones then observes, " The corpuscles 

 of the blood of the Earth-worm are remarkable for their great size, being on 

 an average yjij^dth or y^^j^dth of an inch in diameter. There are both granule 

 and nucleated cells*." 



Investigations of the most extended and scrupulously exact description 

 enable the author here to affirm most confidently that in the account of the 

 corpuscular elements of the blood of the Annelida just cited from the memoirs 

 of Milne-Edwards and Wharton Jones, these distinguished observers have 

 fallen into extraordinary errors. In no single species among the Annelida 

 does the blood-proper contain any morphotic element whatever I In all in- 

 stances, without a single known exception, it is a perfectly amorphous fluid, 

 presenting under the highest powers of the best microscope no visible cor- 

 puscles or molecules or cells whatever ; it is a limpid fluid variously coloured, 

 as originally and correctly described by Milne-Edwards, in different species. 

 No complete distinction into venous and arterial blood can be observed, and 

 the plan of the circulatidn renders such a distinction only partially possible. 

 In all cases the colouring matter is fluidified and uniformly blended with the 

 fluid mass of the blood ; the colour therefore must be developed in the fluid 

 mass, for there exist here no morphotic elements in the blood itself by 

 which the separation of the coloured substances from the peritoneal fluid 

 can be effected, unless indeed the parietes of the vessels of the blood-proper 

 discharge this eclectic function. With one exception, namely, that of Gly- 

 cera alba, in which they are red, the corpuscles of the peritoneal fluid 

 are in all species destitute of colour. But it is not at all chemically impos- 

 sible that the coloured ingredients may exist in this fluid in a colourless 

 state, and that these ingredients, through entering into new combinations, 

 may become brightly coloured after transition into the true blood. In con- 

 sequence of the impracticable minuteness of the quantity, no direct chemical 

 analysis of the blood in the Annelid can be executed. As to the colour, 

 however, analogy removes all doubt that the red tinge is due to the salts of 

 iron, and the green to those of copper. In those species in which the blood 

 is light-yellow, opake, or lymph-like, it does not follow that the salts of the 

 coloured minerals are altogether absent ; they may exist under colourless 

 combinations. The physiologist cannot view with unconcern the question 

 which in this class of animals affects the mode in which the peritoneal 

 fluid and the blood-proper stand related to each other. That the former is 

 higher than the latter in degree of organization no doubt can exist ; but it 

 is not quite clear that the true blood is reproduced out of the elements of the 

 peritoneal fluid ; since the vessels distributed over the parietes of the 

 alimentary canal may take up some of the immediate products of digestion 

 before the latter exude into the general cavity of the body to mingle with its 

 semi-aqueous contents. Nor can it be affirmed, from the evidence drawn 

 from its composition, that the peritoneal fluid is unfitted to supply the 

 means of nutrition to the solid structures, into the interior of which in every 



* Here follows an elaborate account of the metamorphoses which these two varieties of 

 corpuscles undergo ; and with respect to the Leech, Mr. Jones states, " that whilst the corpus- 

 cles of the blood of the Earth-worm are the largest which I have yet found in any vertebrate 

 animal, the corpuscles of the Leech are the smallest." (p. 95, op. cit.) 



