RED VASCULAR FLUID OF THE EARTHWORM. 7*3 



from the walls of the vessels, whilst the granule which takes 

 a deep staining from picrocarmin is the nucleolus. 



In fresh blood-vessels of the Earthworm I have not succeeded 

 in observing the blood-corpuscles. Their small size and delicate 

 character suffices to conceal them in the red-coloured fluid where 

 they float. I first detected them in specimens of the tissues of 

 the earthworm which had been treated with a -j-Vth per cent, 

 solution of osmic acid for half an hour, washed with dilute 

 alcohol, and then stained whilst still under the covering glass by 

 a solution of picrocarmin, and subsequently clarified by 

 glycerin. After such treatment, the finer vessels of the mus- 

 cular septa and of the walls of the testicular sacs of the earth- 

 worm exhibit very clearly the histological elements of their 

 walls, whilst the coagulum within the vessels is seen to contain 

 numerous free corpuscles of the form and appearance above 

 described. The corpuscles occur in the vessels in masses ; fre- 

 quently a large portion of a vessel will be found free from them, 

 whilst an adjacent segment is choked with an abundance. 



In order to observe the blood-corpuscles of the Earthworm in 

 the fresh condition it is necessary to remove on to an object- 

 slide a portion of a large vessel by means of two pairs of forceps, 

 and to allow its contents to escape on to the slide. It is not 

 possible in this manner to avoid all admixture with the perivisceral 

 fluid, the corpuscles of which are very abundant and adhere 

 tenaciously to the tissues bathed by that fluid. It is, however, 

 quite easy to distinguish the blood-corpuscles or corpuscles of 

 the vascular fluid from the lymph-corpuscles or corpuscles of 

 the perienteric fluid by their shape and size. A cleanly prepared 

 drop of perienteric fluid shows large, colourless, vacuolated cor- 

 puscles, with a ragged outline, often produced into filaments, and 

 provided with a large nucleus ; but in such a specimen none of the 

 peculiar oblong, flattened, homogeneous (saving the granule) cor- 

 puscles peculiar to the blood or vascular fluid will be found. Ac- 

 cordingly, when a quantity of the vascular fluid is taken, even 

 though it be contaminated by a few lymph-corpuscles, it is quite 

 easy to recognise the small and peculiar blood-corpuscles. 



It is my intention to figure the blood-corpuscles of the Earth- 

 worm now described, in connection with a description and 

 illustration of a few other points relative to the histology of 

 that animalj which Mr. D'Arcy Power has worked out in the 

 histological laboratory of Exeter College. 



