116 
Proceedings of Royal Society of Edinhurgli, [sess. 
On the Blood of the Invertebrata. By A. B. GrifiB.ths, 
Ph.D., F.E.S.E., F.C.S., &c. 
(Read July 4, 1892.) 
Introduction. 
The blood of the Invertebrata, like that of the Vertebrata, 
is not homogeneous. It consists of a transparent or semi- 
transparent liquid, and a number of small, solid corpuscles which 
float in it. 
In the higher animals the corpuscles are of two kinds- — red and 
colourless ; but in the Invertebrata there are, as a rule, only colour- 
less corpuscles. The red blood of Annelids is different from the 
red blood of Vertebrates, inasmuch as the plasma is coloured, and 
the corpuscles are colourless in the former,"^ while in the latter the 
plasma is colourless, and there are present coloured and colourless 
corjDuscles. 
The corpuscles in the blood of the Invertebrata are of different 
sizes, and the size varies greatly in the same individual. Their 
form, however, is generally spherical, and their surface has a rasp- 
berry appearance. 
In the higher Invertebrata the blood clots after a variable period 
of time. Haycraft and Carlier f have recently examined the coagu- 
lation of the blood in certain Invertebrates. According to their 
investigations “ the clot is formed, at any rate for the greater part, 
by the welding together of blood-corpuscles. These throw out 
processes which interlace to form a solid mass.” 
Although the blood of the Invertebrata contains corpuscles, its 
composition greatly varies. For instance, the blood of the lower, 
and some of the higher, Invertebrates is a watery fluid containing 
only a small amount of proteids. This kind of blood has been 
termed hydrolymph. But in the majority of the higher Inverte- 
brates the blood is less watery, and much richer in proteids. This 
variety of blood is called hsemolymph. The distinction between 
* There are a few exceptions to this general statement, 
t Proc. Roy. Soc. Edin., vol. xv. p. 423. 
