CYCLOPS. 



[ 182 ] 



CYLINDROSPERMUM. 



with a marginal serrated seta (6); each man- 

 dible has also a palpus, consisting of one 

 segment and two long filaments. 



Behind the mandibles, the first pair of 

 foot-jaws (fig. 12) are situated; each consists 

 of a body, convex externally, concave inter- 

 nally, furnished at the end with two or three 

 strong teeth, and with a single-jointed palp- 

 like organ terminated by setae. 



The second pair of foot-jaws (fig. 13 a b) 

 are divided to the base into two portions : 

 an internal (6) smaller, and consisting of 

 four joints, each with one or more setigerous 

 spines, the last with three ; and an external 

 (a) composed of three joints, to the base of 

 the first of which the internal portion is at- 

 tached; this first joint is the longest, and 

 furnished on its inner side with two tuber- 

 cles, each with one or two setigerous spines, 

 a longer jointed spine arising from near its 

 distal extremity; the second joint is fur- 

 nished with two strong claws, of nearly equal 

 size ; and to its upper edge is attached the 

 third joint, smaller than the second, also 

 furnished with two claws ; some of the spines 

 are themselves setigerous. 



There are five pairs of legs or feet, four of 

 which are branchial, uniform, and arise from 

 the thoracic segments. Each of these feet 

 (fig. 14) is composed of two branches arising 

 from a common base ; each branch is three- 

 jointed, and each joint is furnished with ele- 

 gantly plumose setae, the last having six or 

 seven. The fifth pair of feet (fig. 15) are 

 rudimentary, and arise from the first and 

 smallest segment of the abdomen ; they are 

 two-jointed in the female, and three-jointed 

 in the male. 



The external ovary (fig. 9 o) communicates 

 directly with the internal by means of a 

 small canal on each side between the first 

 and second segments of the abdomen. 



The tail consists of two lobes, each termi- 

 nated by four variously setigerous filaments, 

 the two intermediate being the longest, and 

 jointed near their origin; sometimes there 

 are two joints to each, and the outer ones 

 are also jointed. 



Scarcely a pool of water can be found in 

 which this animal may not be seen darting 

 about in various directions. It varies greatly 

 in structure and appearance, according to 

 age, locality, sex, &c., and these varieties 

 have been admitted as so many species by 

 some authors. 



PI. 15. fig. 16 represents a recently hatched 

 Cyclops. 



The individuals are frequently covered 



with Vorticellce and other parasitic Infu- 

 soria. 



BIBL. Baird, British Entomostr. p. 198; 

 Koch, Deutschl. Crustac. &c. 



CYCLOTELLA, Kiitz. A genus of Dia- 

 tomaceae. 



Char. Frustules free or adherent to other 

 bodies, disk-shaped, mostly solitary ; valves 

 circular, flat, convex, depressed or undulated, 

 striated ; striae radiating. 



The frustules of some of the species are 

 immersed in an amorphous gelatinous sub- 

 stance. 



When the valves of (all ?) the species of 

 Cyclotella are examined under an object- 

 glass of large aperture, with the central stop 

 (!NTR. p. xvi. et seq.), the surface is found 

 to be marked with dots or depressions 

 arranged in radiating rows, as in some spe- 

 cies of Coscinodiscus ; hence these two ge- 

 nera should probably be united. Some of 

 the species (?) appear to represent the frus- 

 tules of Melosira seen in end view. 



C. operculata, K. (Pyxidicula operculata, 

 ., Discoplea Kutzingii, E.) (PI. 12. fig. 21 ; 

 a, side view; b, front view). Angles of frus- 

 tules in front view rounded ; striae obscure, 

 very short, giving the margin a punctate 

 appearance;, aquatic; diameter attaining 

 1-1000". 



/3 rectangula, K. (C. Kutzingiana, S.) 

 (PI. 12. fig. 22). Angles of front view not 

 rounded; striae more distinct. 



C.Meneghiniana. Valves plane, distinctly 

 striated at the margin; aquatic; length 

 1-1440". 



/3 major. Twice as broad. 



C. antiqua,$.(Discoplcea atmospherical.}. 

 Valves convex; striae broad, reaching nei- 

 ther the centre nor the margin; aquatic; 

 diam. 1-760". 



Kiitzing characterizes three marine spe- 

 cies, with the valves free from striae, and 

 seventeen doubtful species, marine and fos- 

 sil, belonging to the genera Actinocyclus, 

 Discoplea (?), and Hyalodiscus of Ehren- 

 berg. 



BIBL. Kiitzing, Syn. Diat., Bacill. p. 50, 

 and Sp. Alg. p. 18 ; Ehrenberg, Ber. d. 

 Berl. Akad., passim-, id. Infus., and Mikro- 

 geologie, fyc. ; Smith, Brit. Diat. p. 27 ; 

 Thwaites, Ann. Nat. Hist. 1848. i. p. 

 169. 



CYLINDROSPERMUM, Kiitzing (Ana- 

 baina, Bory and others). A genus of Nos- 

 tochaceae (Confervoid Algae), with the fila- 

 ments radiating less than in the allied Sphee- 

 rozyga ; distinguished under the microscope 



