438 CRUSTACEA. 



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 Juriiie, considered as or^nans of generation, from the manner in which 

 they are used during coupling. Tlie females are provided, on eacli 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 Miiller as forming a distinct genus, named Aiiiymune. Some time aftei-wards 

 (fifteen days in February and March), they acquire another pair of legs, in which state they constitute MiiUer'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—m its shorter antennas, 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 antennae and mandibular palpi divided into two branches, 

 form another division. 

 The subgenus Calanus of Leach is described as having no inferior antennae;— but is this statement original? 

 llie type of the genus is the Cyclops quadricomis (Monociiliis quadricornis, Linn. ; and C. vulgaris, Leach), 

 which has all the antennae 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. 

 The length is cne-fifth of an inch. It is very abundant. 



[W. Baird, Esq., has published a very complete memoir upon this genus in the fourth num- 

 ber of the Magazine of Zoology and Botany, giving the bibliographical history, anatomy, and 

 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 

 gives birth to forty young at a time, may become the progenitor of 4,442,189,120 young ! He 

 has corrected Latreille's observations relative to the genera Amymome and Nauplius, the 

 Fig. i7.-Cycio|i» species of which the former genus was composed consisting of the young of C. minutus in dif- 

 vuitfuris, magnified, fg^pnt states, wbich never assume the form of Nauplius, whereas the Nauplius is the young of 

 C. quadricomis. He considers them to be decidedly carnivorous.] 



[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. [Calamtsl arietis) is remarkable 

 for the o-reat length of its superior antennae, which are armed near the tip with two very long recurved seta;. The 

 Cyclops (Anomalocera) Pattersonii, described by the same gentleman in the second volume of the same work, is 

 closely allied to Cyclops castor. The males of both species are remarkable for having one of the antenna; greatly 

 swollen beyond the middle, the other being simple.] 



[Cetoc/iilus of Vauzeme is a singular genus, difiering from Cyclops in having a pair of eyes. They have two very 

 lono-, and two very short antenna; ; five pairs of short foot-jaws ; five pairs of swimming, bifid, and ciliated legs ; 

 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 Lopliyropa — 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 svvinimeret, accompanied by a branchial 

 l)late. The antennae are simple ; they have only one eye ; the mandibles and anterior maxillae are pro- 

 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. 



Ci/there, MiiU., Cytherina, Lam., has, according to Muller, eight simple legs terminating in a point, and two 

 antenna;, 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 confervae.* [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.— -Vif*/. ofZool. and Bot., ii. 139.] 



Cypris, MiiU., has only sixf legs, and their two antenna; are terminated by a pencil of [long] hairs. Tlie 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 ; nef.rly 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 antennae, affixed immedi- 



, it is not surprising + Fmir, according to Ranidolir, but ciglit, according to Jurint ; tlie 



of tlieir plnce of resi- ' former regarding tiie posterior pair as organs of tlie male sex. and the 

 of Cytliere, confining latter considering tine mandibular palpi, and the branchial plate of 

 ' the superior ma.\ill<E', as legs. 



