ELEDONE. 5O9 
CIRCULATORY SYSTEM. 
In order to dissect the vascular system of Eledone 
adequately, it 1s necessary to inject the vessels. The 
venous system is best injected from the anterior vena 
eava, and the arterial system from the base of the efferent 
blood vessel of one side. As the veins lie more 
superficially than do the arteries, it is best to follow them 
out first. If dissecting one specimen only for all the 
systems, only the main blood vessels, e.g., the anterior, 
abdominal, genital and efferent arteries, the three venae 
cavae, and the veins of the arms, can be followed 
satisfactorily. 
The circulatory system will be described under the 
following headings:— (1) Blood, (2) Heart, (5) Arterial 
system, (4) Venous system. 
The course which the blood follows in the body may 
be briefly summarised as follows :—-Blood which has been 
aerated in the gills returns by means of the two efferent 
vessels to the auricles, and thence into the ventricle of 
the heart. From there it passes out to the body by the 
anterior, posterior and genital aortae, and ultimately 
reaches the arterial capillaries. Thence passing into the 
veins, it finally enters the lateral venae cavae, which take 
it back to the gill, thus completing the circulation. 
BLoop. 
The blood of Eledone is a clear Limpid fluid, of very 
pale blue colour. For examination it may be easily 
obtained by opening the efferent artery, at the base of the 
gill, or the anterior aorta, or again the anterior vena cava. 
In contact with the oxygen of the air the blue colour soon 
deepens. The various constituents of the blood are : — 
(1) Small colourless amoeboid and very granular 
