§ 277. 
THE CRUSTACEA. 
§ 277. 
‘The sense of Sight is present quite universally with Crustacea. 
The Cirripedia, the Penellina, and the Lernaeodea, alone, are without it ; 
and even here this deficiency occurs only during the last phases of their re- 
trograde metamorphosis, when these animals remain fixed to foreign bodies. 
There is, moreover, in the other orders, here and there a genus which 
contains blind individuals. Such is the case with the females of certain 
parasitic Isopoda,® and with some subterranean Myriapoda. 
The eyes of Crustacea present very various grades of development. The 
lowest of these is seen in the so-called Simple-eyes. With these, there is 
observed a convex cornea, and, behind it, a round, light-refracting body. 
This lens is surrounded by a layer of black, brown, red, or blue pigment, 
which, at its most convex point, is perforated by an optic nerve. The 
young individuals of the Cirripedia, the Penellina, and the Lernaeodea, have 
an eye of this kind in the middle of their forehead, but which gradually dis- 
appears in the course of their metamorphosis.” Certain Ergasilina, as 
likewise the Lophyropoda and Phyllopoda, have, also, at their escape from 
the egg, a simple eye, which, with the Ergasilina, and certain Lophyropoda, 
825 
thought them comparable to a cochlea, but he was 
unable to find any nerve going to them, and has 
relinquished this idea,— doubting that these organs, 
and the ampulla mentioned, are really auditive or- 
gans. Farre (loc. cit.) has gone further ; he has 
taken these bodies for olfactory organs, and has 
endeavored to show, as already mentioned, the or- 
gans of smell to be real organs of hearing. It is 
true that, in the orgarts of hearing, no otolites are 
found ; but the principal parts exist, such as a Ca 
“yum tympani, at the entrance of which is extend- 
ed atympanitic membrane and an auditive vesi- 
cle, upon which is spread a nerve. 
The view of Frey (De Mysidis Anat. p. 18), 
then, is inadmissible ; he regards the seat of hear- 
ing, with Mysis, as the two internal caudal valves, 
where he has observed a cavity containing a radi- 
ated body, the nucleus of which has a crystalline 
structure, and which he regards as an_otolite. 
But, aside from the singular structure of this body, 
he does not mention its having any special nerves. 
It is, moreover, unnecessary to seek, with those 
Crustacea whose antennae are highly developed, 
the auditive organs anywhere but on the head; 
for, at the base of these antennae, as, for example, 
with the Amphipoda, there are several other hol- 
low processes which, in part, have been regarded 
as palpi, but which, upon more careful examina- 
tion, will undoubtedly be found to be, some auditive, 
and others olfactory organs. 
Frey and Leuckart (Beitr. p. 114, Taf. II. fig. 
18) have, from the first, described in more detail 
the organs of the caudal valves of Mysis, as 
proper auditory organs ; but, aside from the two 
so-called otolites which, contrary to all analogy, 
are provided with stiff bristles, the correctness o' 
this “nterpretation is always open to question, for 
these authors have been unable to perceive any 
* [§ 277, note 2] Recent investigations have 
disclosed the existence of eyes with the Cirripedia. 
Leidy (Proceed. Acad. Sc. Phil. IV. 1848, No. 1) dis- 
covered them with Balanus, and this discovery has 
led to the confident and successful search of them 
in other genera. With Lepas, according to Dar- 
win (Monograph, &c., loc. cit. p. 49), there are two 
elosely-approximated eyes, forming a double eye, 
28 
nerve destined for these so-called auditive capsules, 
with Mysis. 
1 For the eyes of Crustacea, see especially J. 
Miller, Zur vergleich. Physiol. d.. Gesichtsinnes, 
p. 307 ; ‘or its abstractin Ann. d. Sc. Nat. XVII. 
1829, p. 225, or his later researches on the eyes of 
the Insecta and Crustacea, in Meckel’s Arch. 
1829, p. 88, and in Tiedemann’s Zeitsch. f. Phys- 
iol. IV. p. 97. 
2 The adult Cirripedia, notwithstanding the ab- 
sence of eyes, are very sensitive to light. This I 
have observed with individuals of Balanus pusil- 
lus, which I had captive several weeks at Danzig. 
These animals, when undisturbed, came out of their 
shell, and executed the usual motions of their cirri, 
but they withdrew as quick as lightning into the 
shell, when, from passing my hand over the vessel, 
Ishaded them. Coldstream (Cyclop. loc. cit. p. 
688) has made similar observations.* 
3 The females of Jone, Phryxus, and Bopyrus.} 
4 For example, with Polydesmus, Blanwulus, 
Cryptops, and Geophilus. 
5 For example with Achtheres, Tracheliastes, 
Lernaeocera (Nordmann, loc. cit. p. 80, &c., 
Tab, IV. fig. 5, Tab. VI. fig. 5,6). The Cirripe- 
dia have, at their escape from the egg, a single, 
black eye, according to Thompson ; see the Philos. 
Trans. 1835, p. 355, Owen, Lectures, &c., p. 161, 
fig. 88; and Goodsir, Edinb. new Philos. Jour. 
1843, No. 69, p. 97, Pl. ILI. fig. 8, and Pl. IV. fig. 
13-17 (Lepas aiid Balanus); but with the embry- 
os of Balanus pusillus, I have found this eye of 
aredcolor. The reason why Burmeister (Beitr. 
&c. p. 15, Taf. I. fig. 2) could perceive no eye 
with the young of Lepas, is, as he himself has re- 
marked, because they had been effaced by the 
alcohol in which the specimens examined had 
long been preserved. 
situated at the extremity of two optic nerves which 
proceed each from an ophthalmic ganglion. These 
ganglia are situated on two nervous cords which 
arise from the supra oesophageal ganglia. — Ep. 
t [§ 277, note 3.] Quite remarkable among the 
blind Crustacea is the Astacus pedlucidus Telk. 
from the Mammoth Cave, Kentucky. — Ep. 
