630 
UK. T. WILLIAMS ON THE BLOOD-PROPER AND 
Like that of the latter it abounds little in organic corpuscles, and the general ap- 
pearance is like that of pure water. The morphotic elements consist of groups of 
formless granules. The diverticula of the digestive system are so arranged as to be 
surrounded within by the peritoneal fluid and without by the external water, which 
is drawn in through the meshes of the felt. This arrangement proves obviously that 
the contents of the digestive caeca are expressly in this Annelid exposed to the action 
of the two fluids described. These ‘contents’ consist of a dark olive fluid, and 
though destitute of organic bodies, is endowed with nutritive properties. 
In this Annelid, therefore, as in the Leech, the fluid contained in the digestive sac- 
culi is the true equivalent of the chylaqueous fluid of the peritoneal cavity of other 
species. In the Leech this latter cavity is almost obliterated, in Aphrodita it is 
spacious and occupied by a fluid, colourless and limpid as water. Moreover, in 
Aphrodita, the peritoneal cavity is distinguished from that of all other Annelids by 
the fact that it is lined by vibratile epithelium, in which respect it is allied to the 
Echinoderms. The fluid which fills the digestive caeca in Aphrodita contains no 
determinately organized solid bodies, another respect in which it resembles that of 
the diverticula of the stomach of the Starfish. The blood-proper in this aberrant 
Annelid is perfectly fluid, devoid, that is, of all morphotic elements, and yellowish in 
colour. 
In no case in the animal kingdom is the physiologist presented with a more favour- 
able opportunity for determining the real meaning of the floating cells of the nutri- 
tive fluids than that which occurs in the Annelida. Here nature performs for him 
the difficult experiment of separating the albumen and fibrine-producing from the 
colour-producing parts of the vital fluids. It has been demonstrated that in every 
Annelid the chylaqueous fluid is more or less corpusculated. In every species this 
fluid and its corpuscles have been found to be colourless-, two exceptions only in the 
whole class were encountered. The chylaqueous fluids of Clymene arenicoida and 
Glycera alba were found to be charged with blood-red corpuscles, the fluid in which 
they floated being colourless. Here is an unequivocal demonstration that the invo- 
lucrum of the floating cell is capable of separating from a colourless fluid a pigmented 
fluid, the blood-red contents of the cells ! But what can become of the red fluid with 
which these floating cells are filled ? If the cells dehisce while yet in the chylaqueous 
fluid, the latter ought to exhibit a tinge of the same colour, which is not the case. 
Further observations are required to track with accuracy the vicissitudes which these 
singular bodies undergo, but which are singularly calculated to unfold the tale of the 
real changes which all floating corpuscles are destined to suffer in fulfilment of their 
peculiar functions. 
Blood-proper in the Annelida, and its physiological relations . — Cuvier, Lamarck, 
De Blainville, Pallas, Savigny and Milne -Edwards, amongst continental natu- 
ralists, have contributed observations on this subject. The discovery of red blood iu 
