COCCOLITHE. 



L 187 j 



COCCONEIS. 



these large cells become free from the gene- 

 ral frond, and lav the foundation of new 

 ones, originally of definite form, which in- 

 crease in size by the division of the indivi- 

 duals within a persistent gelatinous invest- 

 ment. Brebisson, Ralfs, and Braun describe 

 a process of conjugation in C. BreUssonii 

 (PL 7. fig. 6). Two cells come into contact, 

 and their membranes become fused ; the 

 intermingled contents then undergo a meta- 

 morphosis, brownish oil-globules replacing 

 the chlorophyll ; and the ' spore-cell ' thus 

 produced passes through a period of rest 

 before resuming its vegetative development. 

 Thwaites states that the slender filamentous 

 bodies sometimes found in the frond are 

 part of the organization of the plant (see 

 PALMELLACEJE). Several British species 

 are described : 



C. protuberans, Spreng. Frond green, 

 irregularly lobed, spreading on the ground, 

 cells elliptical, about 1-3000", enlarged vesi- 

 cles 1-500 to 1-1000". Hassall, Alga, pi. 76. 

 fig. 7, pi. 82. figs. 6-10 ; Palmella protube- 

 rans, Grev. Sc. Crypt, Fl. pi. 243. fig. 1. 



C. muscicola, Meneghini. Hassall, /. c. 

 pi. 78. tigs. 3 a, 3 b. 



C. hycilina, Menegh. Fresh water. Hass. 

 /. c. pi. 78. figs. 2 a, 2 b. 



C. depressa, Menegh. Hass. 1. c. pi. 78. 

 figs. 4 a, 4 b. 



C. Mooreana. Hass. 1. c. pi. 78. 1 a, 1 b. 



C. riwlaris. Hass. /. c. pi. 78. 6 a b. 



C. Grevillei, Hass. Frond minute, dense- 

 ly crowded, globose or somewhat lobed, 

 green. In healthy moist situations, fre- 

 quent. Hass. /. c. pi. 78. tigs. 7 a b and 8 ; 

 Palmella brotryoides, Grev. Sc. Crypt. Fl. 

 pi. 243. fig. 2. 



The plants are not yet satisfactorily un- 

 derstood ; the relations to Palmella and 

 Glceocapsa are confused. 



BIBL. Meneghini, Monogr. Nostoch. ; 

 Kiitzing, Phyc. gen. ; Braun, Rejuv. (Ray 

 Soc. 1853), as Palmoglcea ; Thwaites, Aim. 

 N. H. ser. 2, vol. ii. 312 (as Palmella) ; 

 Nageli, Einzell. Algen, 1849 ; Rabenhorst, 

 Fl. Alg. ii. 67. 



COC'COLITHE or COCCOLITE. A 

 term applied to the granular varieties of 

 pyroxene (native silicate of magnesia, with 

 metallic silicates). 



COC'COLITHS. The name given by 

 Huxley in 18u8, to minute oval or round, 

 calcareous bodies (PL 23. fig. 56 b), 1-900" 

 aiid less in size, abounding in the Atlantic 

 ooze, either loose or attached to small lumps 

 of protoplasm (' Coccospheres,' Wallich). 



Two forms were recognized, Discolithi and 

 Cyatholithi. Similar microliths had been 

 noticed as forming a large proportion of 

 white chalk by Ehrenberg, Reade, and 

 Sorby. Wallich also found them in the 

 North Atlantic, in chalk, in tropical float- 

 ing Coccospheres, and in dredgings in the 

 English Channel. Haeckel subsequently 

 found them in the harbour of Lanzarote, 

 Carter in the English Channel, and Guem- 

 bel in limestones of all ages. 



Ehrenberg termed these little bodies 

 ' Morpholites of the chalk,' and regarded 

 them, like his l crystalloids,' as due to the 

 rearrangement of calcareous particles. Sor- 

 by, Huxley, Wallich, and Haeckel differ in 

 opinion as to whether they exist indepen- 

 dently or not of Coccospheres. Carter 

 ascribes them to an Alga (Melobesid). 



Coccoliths of either kind, treated with, 

 dilute acid, leave a soft flexible cast or film, 

 which is coloured yellow by iodine, pale 

 red with carmine, red by Millon's test, and 

 is dissolved by alkalies. 



BIBL. Ehrenberg, Monatsber. Ak. Berlin, 

 1836 ; Pogg. Ann. 1836, xxxix. 101 ; Ab- 

 handl. Ak. Berlin, 1838, 67 ; N. Jahrb. f. 

 Min. 1840, 680; Journ. prakt. Chemie, 1840, 

 xxi. 95 ; Edin. N. Phil. Journ. 1841, xxx. 

 353 ; Mikrogeologie, 1854 ; Reade, ManteWs 

 Wonders of Geology, 7th ed. ii. 953 ; Huxley, 

 Deep-sea Soundings, fyc. 1858, 64 ; Qu. Mic. 

 Journ. 1868, 203 ; Wallich, Life at Great 

 Depths, 1860, 13 ; Ann. Nat. Hist. 1861, 

 vii. 396, ibid. viii. 52 ; Sorby, Proc. Lit. 

 Phil. Soc. Sheffield, 1860 ; Ann. N. H. Sept. 

 1861 ; Haeckel, Jen. Zeitschr. v. 1870 ; 

 Guembel, Jahrb. Munch. 1870, 753 j Carter, 

 Ann. N. H. 1871, vii. 184. 



COCCONETS, Ehr. A genus of Diato- 

 maceae. 



Char. Frustules single, depressed, adnate; 

 valves elliptical, one of them with a median 

 line and central nodule. 



The valves are mostly covered with dots 

 (minute depressions), appearing like lines 

 under a low power. 



The upper valve differs from the adnate 

 one in not being furnished with the central 

 nodule : under a low power it appears to 

 have a median line as well as the adnate 

 valve ; but this, in some at least, arises from 

 the dots or markings at this part being more 

 closely in contact than elsewhere. 



The frustules are often found densely in- 

 crusting filamentous Algae. 



C. pediculus (PL 16. fig. 17). Frustules 

 very slightly arched (front view) ; valves 



