446 



Div. 3. ARTICULATA.^CRUSTACEA. 



Class 1. 





riif. 24. — Art;vlus fijiaceus. 

 the rtiiimal iiil^iiiiu-ti ; '2, 



Argulus, Miill., at first named by me 0;:olus, but not sutficiently describecL The young-er J urine subsequently 

 examined the .species which is the t\-pe of the genus, with the most scrupulous attention, obsen'ing it in all its 

 stages. The shield is oval, notclied posteriorly, covering the body, with the exception 

 of the posterior extremity of the abdomen, and supporting', on a triangular frontal 

 space termed the clypeus, two eyes, four very minute antenna.', nearly cylindrical, 

 ])laced in front— of which the superior, very short and 3-jointed, have, at the base, a 

 strong, toothless, recun'ed hook, and of which the inferior are 4-jornted, with a small 

 tooth upon the basal joint. The siphon is directed fornards. The legs are twelve in 

 number. The two anterior are terminated by a large limb, circularly dilated at the tip, 

 and striated and toothed at the edge; exhibiting, on the inside, a kind of rosette, 

 formed by the muscles, and seeming to act as a sucking-cup. Tliose of the second pair 

 are fitted for prehenaion, with tlie thighs thick and spinose, and the tarsi composed of 

 of the iar,;e interior smkiiiK. thrcc joiuts, tiic last of which is terminated by two hooks. The other feet are termi- 

 !'."■'''•' "'° ^''''"'"' '*' '""'"'' nated by a swimmeret formed of two fingers, or elongated pinnulae, fringed wth bearded 

 threads. Tlie third pair of legs has an extra finger, but which is recun'ed. Tlie last 

 pair of legs is attached to that part of tlie body which is disengaged behind the shield, or the tail. The abdomen — 

 regarding it as the part of the body extending backwards between the ambulatory feet, the beak, and a tubercle 

 inclosing tlie heart— is entirely free from the place of its insertion, without distinct articulations, and tenninates 

 immediately behind, the two last feet in a kind of tail, in tlje shape of a rounded, deeply-notched plate, without 

 hairs at the tip. It is a kind of swimmeret. Tlie transparency of the integuments permits the heart to be perr 

 ceived. it is situated behind the base of the siphon, lodged in a solid tubercle, semitransparent, and in the form 

 of a single ventricle. 



nie eggs are oval, and of a milky white colour : they are attached by gluten to stones or other hard substances, 

 cither in one or two rows, to the number of fi'om one to foyr hundred. The eggs hatch about thirty-five days after 

 they are deposited ; and the young ones, on bursting forth, are only three-eighths of a line long. Their general 

 form is similar to tliat of the adult state, but the locomotive organs exhibit essential difl'erences. Miiller described 

 the animal in this state as a distinct species, named Argulus Charon. Four long oar-like arms, two placed before 

 and two behind the eye, each terminated by a brush of flexible hairs, which the anhnal moves simultaneously, and 

 by the help of which it swims easily, with a Jerking motion, arise from the anterior extremity of the body. The 

 rudiments of the antenna; are also visible. Tlie two large sucker-like feet are replaced by two strong legs elbowed 

 near the extremity, and terminated by a strong claw, with which the animal affixes itself to fishes. Of the othei 

 legs which appear in the adult state, those only of the second and third pairs, or the two ambulatory feet, and the 

 two anterior oatatorj' legs, are the only ones which are developed and free : the following are, as it were, lapped up, 

 and applied against the ahdomen. Tlie first moulting, which is eflected by means of a rupture of the skin on the 

 under-side of the body, having taken place, the oar-like limbs disappear, and all the natatory legs become disen- 

 gaged. Three days afterwards, tbe second moult takes place, which does not produce any important change ; but 

 at the third moult, which takes place two days aftenvards, we begin to perceh-e the formation of the suckers of the 

 fore-legs. At the fourth moult, which also takes place at the end of two days, these legs have assumed the sucker 

 shape, preserving, however, the terminal hook. At the end of six days, there is another change of the skin, when 

 the organs of generation become apparent; but there still remains another moult, retarded for six days, befort 

 these animals are fitted for reproduction. Thus tlie period of their metamorphoses extends to twenty-five days. 

 They have then, however, attained only half their size. Other inoultings, which take place every six or seven daySj 

 are necessary for their arriving at their full growth. Jurine asserts that the females do not become parents with- 

 out the presence of the males. Those which he kept isolated died of a disease which manifested itself in numerous 

 brown globules, arranged in a semicircle towards the posterior part of the clyi)eus. 



The only species of this genus known [to Latreille] {Argulus fol'taceui;, Jurine; Monoculus folinceus, Limt.; 

 Argulus delpldnus, and A. Charon, Miiller ; Monoculus Gp-ini, Cuvicr ; Ozolus Gasterostei, Latr.) attaches itself 

 to the under-side of the body of the young of Frogs, Sticklebacks, &c., and sucks their blood. Its body is flattened, 

 of a greenish-yellow colour, and iibout two lines and a half long. The younger Herman, who has well described 

 this crustaceous insect in its perfect state, and who cites a manuscript of L. Ualdaner, a fisherman of Strasburg, 

 of the date of 1666, where the same animal is figured, says that, in the neighbourhood of that city, it is only found 

 upon the trout, which it destroys, especially in fish-ponds. It is also found upon the perch, pike, and carp. He 

 says it has never been found upon the gills of the fish. This animal turns itself ab nit 

 in the water in a similar manner to the Gyrini, He says its body is divided into five 

 somewhat indistinct segments along the back. 



[A most elaborate memoir, containing the description of Argulus Catoslomi, an 

 American species of this genus, has recently been published by Messrs. Dana and 

 Herrick, in Si/liinan's Journal.] 



Caligus, Miill., are destitute of the sucker-like feet. The anterior legs are furnished 

 with hooks: the others are divided into a greater or less number of pinnule, or are in 

 the form of membranous leaflets. The shell leaves a considerable part of the body ex- 

 posed, which is terminated posteriorly, in the majority, by two long filaments, and in 



others by appendages in the form of fins or styles. The space between these appendages pig. 2S.— Ci;i>ui fimnm, Linn, 

 also often exhibits various other minute ai)pendages. 



The name of fish-lice, under which these animals are collectively known, indicates 

 that their habits are the same as those of the other S'ipbo'iostoraa. Many naturalists have considered the tubular 



(t, one of the fourth {litir of If.ftx 

 bj one of the third pair uf Icf^s. 



