CRUSTACEA. 
438 
they form a current in the water. In the males, both or one of them are constricted and knotted. The upper an- 
tennae were, previous to the researches of Jurine, considered as organs of generation, from the manner in which 
they are used during coupling. The females are provided, on each side of the tail, with an oval sac, or external 
ovary, filled with eggs, and attached by a very slender peduncle. A single act of impregnation is sufficient for 
several successive generations. The female is able to produce as many as ten broods in the course of three 
months. At their birth, the young have only four feet ; and the body is rounded, and destitute of a tail. These 
individuals were considered by Muller as forming a distinct genus, named Amymone. Some time afterwards 
(fifteen days in February and March), they acquire another pair of legs, in which state they constitute Miiller’s 
genus Nauplius. After the first moulting, they have the same form and organs as the perfect insect, but the 
latter are of smaller size. After two more mouitings, they are able to propagate their species. The majority of 
these Crustacea swim back downwards, darting about with great agility, and moving both backwards and for- 
wards with equal ease. In the absence of animal matter, they attack vegetable substances. 
Cyclops staphylinus — in its shorter antennae, which vary in the number of their Joints, and in the gradual nar- 
rowing of the body, as well as in the curved corneous point with which the under-side of the base of the tail is 
armed — forms a separate division in the genus. ■ 
Cyclops castor, and some other species, having the antennse and mandibular palpi divided into two branches, |i 
form another division. 
The subgenus Calanus of Leach is described as having no inferior antennse ; — but is this statement original? 
ITie type of the genus is the Cyclops quadricornis (Monoculus quadricornis, Linn. ; and C. vulgaris, Leach), 1 
f which has all the antenna single, and not divided. The body is ovoid, and the tail six-jointed. , 
The colour varies considerably, some individuals being reddish, others whitish or greenish, j 
The length is one-fifth of an inch. It is very abundant. I 
[W, Baird, Esq., has published a very complete memoir upon this genus in the fourth num- i 
ber of the Magazine of Zoology and Botany, giving the bibliographical history, anatomy, and jj 
economy of the genus, with a monograph of the British species, in great detail. He has given, 
after Jurine, a calculation, whereby it appears, that at the end of one year, a female which j 
gives birth to forty young at a time, may become the progenitor of 4,442,189,120 young ! He i 
has corrected Latreille’s observations relative to the genera Amymome and Nauplius, the || 
Fig. 17 .— Cyclops species of which the former genus was composed consisting of the young of C. minutus in dif- ^ 
vulgaris, magnified. fgj.gnt states, which never assume the form of Nauplius, whereas the Nauplius is the young of j 
C. quadricornis. He considers them to be decidedly carnivorous.] I 
[Mr. Templeton has described some beautiful species belonging to this genus, in the first volume of the Trans- \ 
actions of the Entomological Society, from the Island of Mauritius. One species {C. \_Calanus'] arieiis) is remarkable 
for the great length of its superior antennse, which are armed near the tip with two very long recurved setse. The 
Cyclops {Anomalocera) Pattersonii, described by the same gentleman in the second volume of the same work, is i 
closely allied to Cyclops castor. The males of both species are remarkable for having one of the antennse greatly ■ 
swollen beyond the middle, the other being simple.] 
[Cetochihcs of Vauzeme is a singular genus, differing from Cyclops in having a pair of eyes. They have two very 
long, and two very short antennse ; five pairs of short foot-jaws ; five pairs of swimming, bifid, and ciliated legs ; I 
and a small, narrow, 5-jointed abdomen. Type, Cetochilus australis (Vauzeme in Ann. Sci. Nat., 1834), a species 
found, in inconceivable profusion, beyond 42 of south latitude, in the Pacific and Atlantic Oceans, giving the sur- 
face of the sea a red tint, and serving as the food of the whales.— See Brit. Cyclop. Nat. Hist., vol. i. p. 796.] 
The second general division of the Branchiopoda Lophyropa — that in which the shell is formed 
of two valves united by a fleshy hinge, and inclosing the body when in inaction — have only six [or 
eight] legs, none of which are terminated by a branching swimmeret, accompanied by a branchial i 
plate. The antennse are simple ; they have only one eye ; the mandibles and anterior maxillse are pro- i 
vided with a branchial plate ; and the eggs are carried beneath the back. These compose our Ostra- 
coDA, or the order Ostrapoda of Strauss, and consist of two subgenera, of which the first, Cy there, 
appears to require a more minute examination than has been given to it by Miiller, who is our only 
authority, especially since the elaborate researches of Strauss upon the second subgenus, Cypris. 
Cythere, Miill., Cytherina, Lam., has, according to Muller, eight simple legs terminating in a point, and two 
antennse, also simple, setaceous, 5 or 6-jointed, with hairs scattered upon them. The species are found in 
salt and brackish water, near the shores of the sea, amongst sea-weed and confervse.* [Mr. Baird, who has care- 
fully examined the structure of these animals, states that they have decidedly eight feet and two antennae, and 
that they are only found in sea water.— of Zool. and Bot., ii. 139.] 
Cypris, Miill., has only sixf legs, and their two antennae are terminated by a pencil of [long] hairs. The shell 
is in the form of an oval body, compressed at the sides, arched and swollen at the back, or part where the hinge 
is placed ; nearly straight, or a little incised and kidney-shaped, on the other side. In front of the hinge, and in 
the mid-line of the body, the single eye forms a large black and round spot. The antennas, affixed immedi- 
* If these Entomostraca be exclusively marine, it is not surprising + Four, according to Ramdolir, but eight, according to Jurine ; the 
that Jurine and other observers, in consequence of their place of resi- I former regarding the posterior pair as organs of the nrale se.v, and the ' 
dence, should not have spoken of the species of Cythere, confining latter considering the mandibular palpi, and the branchial plate of 
tlieir attention to the soft water species. ' the superior ma.xillae, as legs. 
