126 
ANN ELIDES. 
sects; for as the nutritive fluid is not contained in vessels* * * § , and 
could not be directed towards pulinonar}^ organs in search of air, it 
was requisite that this air should be diffused throughout the body to 
reach the fluid. This is also the reason why insects have no secretory 
glands, but are provided with mere spongy vessels, which, by the 
extent of their surface, appear to absorb the peculiar juices they are 
to produce, from the mass of the nutritive fluid 
Insects vary infinitely as to the form of the organs of the mouth, 
and those of digestion, as well as in their industry and mode of life ; 
the sexes are always separated. 
The Crustacea and Arachnides were long united with the Insecta, 
under one common name, and resemble them in many points of their 
external form, in the disposition of their organs of motion, and of 
the sensations, and even in those of manducation. 
CLASS 1. 
ANNELIDESj. 
The Annelides are the only invertebrate animals that have 
red blood. It circulates in a double system of complicated 
A'essels §. 
Their nervous system consists in a double knotted cord, like that 
of insects. 
Their body is soft, more or less elongated, and divided into a, fre- 
quently, considerable number of segments, or at least of transverse 
plicae. 
They nearly all inhabit the water — the Lumbrici or Earth-worms 
excepted ; several penetrate into holes at the bottom, or construct 
* M. Carus has observed regular movements in the fluid which fills the bodies of 
certain larvae of Insects ; hut this movement does not take place in a system of 
closed vessels, as in the superior animals. See his treatise entitled “ Discovery of a 
simple circulation of the Mood, &c.” in German, Leipsic, 1827, Ito. 
-f- On this subject see my Memoir on the nutrition of Insects, printed 1799- 
Mem. de la Soc. d’Hist. Nat. de Paris. Baudouin, an vii, 4to, p, 32. 
X I established this class, distinguishing it by the colour of its blood and other 
attributes, in a Memoir read before the Institute in 1802. See Bullet, des Sc.. 
Mesidor, an X, where I described the organs of the circulation. 
M. Lamarck has adopted and named it, Annelides. Brugieres previously united 
it to the order of the intestinal worms, and before him, Linna;us placed part of these 
animals among the Mollusca, and the rest among the Intestini. 
§ It has been asserted that the Blood of the Apliroditae is not red. I think I 
have observed the contrary in the Aphrodita sqiiarnata. 
