637 



BRANCHIOPODA. 



BRANCHIOPODA. 



653 



its entire length. The tail consists of seven rings. The posterior 

 antennae (antennules of Jurine) are tolerably large and composed of 

 four joints, the anterior antennae are thrice the length of the posterior. 



There are several varieties. 



Var. a. Reddish ; eggs brown, forming two oblique masses near 

 the sides of the tail. Total length eight-twelfths of a line. This is 

 the Monoculus quadricoiiiis rubens of Jurine. 



Var. 6. Whitish or gray, somewhat tinged with brown, rather 

 larger than the preceding. Egg-masses greenish, forming nearly a 

 right angle with the tail. Total length the same as the preceding. 

 This is the M. q. albidus of Jurine. 



Var. c. Greenish. Direction of the two egg-masses intermediate 

 between that of the egg-masses of the two former. Length nine- 

 twelfths of a line. M. q. mridis of Jurine. 



, Cyclop* tulgarit, magnified. 



1, Male of variety a ; 2, female of the same; a a, antenna?; b b, sexual 

 organs of the male ; c c, external oviparous pouches of the female ; d d t internal 

 oraries ; 3, a female of variety c ; 4, a young individual of that variety. 



Var. d. Smoky red. General form nearly oval. Eggs brown, com- 

 posing two masses, which cover a great portion of the tail. Length 

 six-twelfths of a line. M. q. fucu of Jurine. 



Var. . Of a deeper green than var. c. Eggs obscure green, passing 

 a little into rose-colour when hatching is near, forming two masses 

 attached to the tail, and appearing to be incorporate with it. Length 

 the same as the preceding. M. q. prarimu of Jurine. 



Oitracoda, Latreille ; Oitropoda, Straus. 



The shell of the Oitracoda is formed of two pieces or valves repre- 

 senting those of a couchiferous mollusk or bivalve shell, but horny, 

 not testaceous. As in the bivalves, the two pieces are united by a 

 hinge, and when the animal is inactive they close upon and shut in 

 the body and the parts. The feet are ambulatory, six in number, and 

 none are terminated by a digitated swimming organ, nor accompanied 

 by a branchial lamina. The antennae are simple, filiform, or setaceous. 

 There is but one eye, which is composite and sessile. The mandibles 

 and jaws are furnished with a branchial lamina, and the eggs are 

 situated on the back. 



In this division Latreille includes the genera Cythere, Miiller (Cythe- 

 rintt, Lamarck) and Cyprii. Cythere has one eye; three pairs of feet; 

 abdomen short ; the inferior or pediform antennae furnished with one 



NAT. HUT. DIV. VOL. I. 



tolerably long curved and jointed filament. The species are inhabit- 

 ants of the sea. They have not the power of swimming, but are always 

 walking among the leaves or branches of the Conferva and Fuci, 

 where they delight to dwell. When shaken out of their hiding places 

 into a tumbler or bottle, they may be seen to fall in gyrations to the 

 bottom, without ever attempting to dart through the fluid, as would 

 be the case with the species of Cypris. Upon reaching the bottom they 

 open their shells and creep along the surface of the glass ; but when 

 touched or shaken they immediately again withdraw themselves within 

 their shell and remain motionless. Dr. Baird, whose work ou the 

 British species contains a fund of information on the habits of the 

 minute family to which these creatures belong, says that the species 

 " are undoubtedly numerous, and the labours* of any inquirer after 

 them would assuredly be rewarded with success." He has described 

 fifteen species as inhabitants of the British coasts. Several of the 

 species have been found fossil. 



Cypris has two pairs of feet, one pair always inclosed within the 

 shell. The two antennas are terminated by a pencil of fine hairs. 

 The case or shell is suboval, arched, and protuberant on the back or 

 hinge side, and nearly straight or a little sinuous or kidney-shaped on 

 the opposite edge. A little in advance of the hinge, and upon the 

 mesial line, is the single large blackish round eye. The antennae, 

 which are inserted immediately below, are shorter than the body, 

 setaceous, composed of from seven to eight joints, of which the last are 

 the shortest, and terminated by a pencil of twelve or fifteen fine hairs, 

 which serve as swimming organs. The mouth is composed of a cari- 

 nated labrum ; of two large toothed mandibles, each furnished with 

 a feeler of three joints, to the first of which a small branchial lamina 

 of five digitations (interior lip of Ramdohr) is attached, and of two 

 pairs of jaws ; the two upper, which are much the largest, have on 

 their internal border four moveable and silky appendages, and exter- 

 nally a large branchial lamina pectinated on its anterior edge ; the 

 second are formed of two joints, with a short, nearly conical, and 

 jointless feeler, also silky at the end. A sort of compressed sternum 

 performs the ofiice of a lower lip (external lip of Ramdohr). The feet 

 have five joints, the third representing the thigh, and the last the 

 tarsus ; the two anterior ones, much stronger than the rest, are inserted 

 below the antennae, directed forwards with stiff hairs on long hooks 

 collected into a bundle at the extremity of the two last joints : the 

 four following feet are without these appendages. The second pair, 

 situated on the middle of the under side of the body, are directed 

 backwards, curved, and terminated by a long strong hook bent for- 

 wards; the two last, never showing themselves beyond the shell, 

 are applied to the sides of the body for the purpose of sustaining the 

 ovaries, and are terminated by two very small hooks. There is no 

 distinct joint observable in the body, which terminates posteriorly in 

 a kind of tail, which is soft and bent upon itself underwards, with 

 two conic or setaceous filaments fringed with three silky hairs or hooks 

 at the end, and directing itself backwards so as to project beyond the 

 shell. The ovaries form two large vessels, simple and conical, situated 

 upon the posterior sides of the body under the shell, and opening, one 

 at the side of the other, at the anterior part of the abdomen, where 

 the canal formed by the tail establishes a communication between 

 them. The eggs are spherical. 



These animals swim with more or less rapidity in the still fresh 

 waters or gently-running streams which they inhabit, in proportion as 

 they bring into action the filaments of the antennae ; sometimes they 

 only show one, at others they put them all forth. Latreille thinks 

 that these filaments may also assist in respiration. The two anterior 

 feet are moved with the same rapidity as the antennae when the 

 animal is swimming ; when it creeps over the surface of the water- 

 plants, the progress is slow. The female deposits her eggs in a mass, 

 fixing them by means of a glutinous substance on the water-plants or 

 on the mud. Anchored by her second pair of feet, so as to be safe 

 from the agitation of the water, she is occupied about two hours ill 

 this operation, the produce of which, in the largest species, amounts 

 to 24 eggs. Jurine collected some of these at the time of their 

 exclusion, and, after having insulated them, obtained another generation 

 without the intervention of the male. A female which laid her eggs 

 on the 12th of April changed her skin six times between that day and 

 the 18th of May following. On the 27th of the last-named month 

 she laid again, and, two days afterwards, made a second deposit. 

 Jurine concludes that the number of moults in the young state 

 corresponds with the gradual development of the individual. 

 Desmarest considers that they do not undergo a metamorphosis, but 

 that they present on their exclusion from the egg the form which they 

 preserve throughout their life. Their food is said to consist of dead 

 animal substances and of Conferva. In summer, when the heats have 

 dried up the pools, they plunge into the humid mud, and there 

 remain in an apocryphal kind of existence till the rains again restore 

 them to activity. 



The recent species are numerous ; Jurine described 21. Dr. Baird 

 describes 15 species as British. 



The hard shells of Cyprit resist decomposition, hence many are 

 fossil. 



Cyprii Paba, Desmarest, holds a place among the organic remains 

 of the Wealden Rocks of England. Dr. Fitton has recorded it in the 

 Weald Clay of the Isle of Wight, Swanage Bay, &c., and Dr. Mantell 



2 u 



