§ 150. THE ANNELIDES. 16E 
often very prominent tactile organs, in the form of processes of variable 
number and shape, which are situated principally though not entirely upon 
the cephalic extremity of the body. Those upon the head have been 
named Antennae, and the others Cérri. These last are often very numer- 
ous upon the first segment of the body. Both are contractile and usually 
unarticulated, though sometimes having very distinct joints. The an- 
tennae receive their nerves directly from the cerebral ganglion, while 
those of the cirri of the first segment, are given off from the base of the 
two lateral cords of the esophageal ring, and from the first ventral gan- 
glion.© : 
IT. Organs of Vision. 
» § 150. 
With nearly all the Capitibranchiati,® and with many Nemertini, and 
Lumbricini, the eyes are wanting. But, as visual organs, have been re- 
garded the brown or black dots, which are two in number with many Nais, 
four with Tetrastemma, but are innumerable and arranged irregularly or 
in rows upon the neck, with Polystemma and Nemertes. 
But these are 
scarcely more than simple pigment dots.” 
With the two to ten eye-specks of the Hirudinei,® however, the structure 
is quite different. 
Here the eye“ is composed of a transparent cylindrical 
body, a little attenuated and rounded at its inferior extremity, while the oppo- 
site one causes the skin to bulge out like a cornea. 
8 The antennae of the Annelides have been dis- 
tinguished from those of insects by being termed 
Tentacula ; for they are non-articulated, while 
those of insects are articulated. But this distinc- 
tion is not valid, for, with the Branchiati, there are 
insensible transitions from the non-articulated ten- 
tacula to the articulated antennae. But another 
and more essential difference is, that those of the 
Annelides are contractile, while those of insects are 
not. These organs are articulated with Eunice, 
Peripatus, and Syllis. In this last it is true of 
the cirri also. The modifications and varieties of 
the antennae and cirri belong, however, to the 
province of Zoology. 
4 With Nerets, four nerves pass off from the 
anterior portion of the brain to the four antennae ; 
the two external as gustatory nerves and which go 
to the larger antennae, are largely swollen at their 
extremity ; see Rathké, De Bopyro et Nereide, p. 
43, Tab. IT. fig. 4, 5. 
5 See Rathké, Ibid. Taf. II. fig. 18, d. d. and in 
the Danzig. Schrift. loc. cit. p. 76, Taf. V. fig. 14, 
d. d 
1A remarkable exception to this occurs with 
Amphicora Sabeila as described by Ehrenberg 
(Mittheil. aus d. Verhandl. d. Gesellsch. naturf. 
Freunde zu Berlin, 1836, p. 2). It has, it would 
* 1 §150, note 1.] Quatrefazes (Ann. d. Se. 
Nat. X. 1848, p. 48, Pl. II. fig. 10, y.) describes 
two colored points situated on the middle of the 
brain of Hermedia, as eyes. They are composed 
of pigment and rest directly on the nervous sub- 
stance. — Ep. 
t [§ 150, note 2.] Quatrefages (Compt. rend. 
14% 
Its remaining portion is. 
appear, two eyes not only at the cephalic extremity,, 
but at the opposite one also.* 
2 Gruithuisen (Nov. Act. Acad. Nat. Cur. XI. p. 
242) has described the two eyes of Nats probosci- 
dea as particles of pigment enveloped by a sensi~ 
tive parenchyma. But this is not based upon ob- 
servation, aud is an hypothesis only, as Muller 
has very judiciously remarked (Ann. d, Sc. Nat. 
XXII. 1831, p. 20). The assertion of Quatrefages 
is of more weight (Comp. rend. XIX. 1844, p. 195). 
He attirms that the pigment specks of many Ne- 
mertini and of a marine species allied to Mais, cop— 
tain really light-refracting bodies, and connect 
with the nervous centre by particular nerves. 
The last of these Annelides has similar pigment 
specks also upon each side of the segments of the- 
body, which receive each a distinct nerve from the 
ventral marrow. Is not this species identical with. 
the Nais picta described by Dujardin (Ann. d. 
Sc. Nat. 1839, XI. p. 293, Pl. VII. fig. 9)? ¢ 
3 Clepsine has two, four or six eyes; Nephelis, 
eight; and Haemopis and Sanguisuga, ten ; 
while with Branchiobdella, they are wanting. 
With this family (the Hirudinei), these organs are 
always symmetrically arranged upon the neck. 
4 Atleast with Sanguisuga officinalis. 
Dec. 31, 1849) has found very pertect eyes with 
Torrea vitrea, consisting of a crystalline lens, a 
choroid coat, a vitreous humor, a transparent cor- 
nea, &c. He thinks also that he has discovered 
with Sabella eyes situated on the branchiae!— 
Ep. 
