CLBIACOSPHENIA. 



[ 183 ] 



CLOSTERIUM. 



'2 scalariform dissepiments ; valves striato- 

 punctate, coslae none. 



C. Lorenzii. Valves linear-lanceolate, 

 swollen at the ends and the middle. In the 

 Adriatic. 



BIBL. Grunow, Wien. Verhandl. 1862, 

 421, pi. 8. fig. 7. 



OLIMAOOSPHE'NIA, Ehr. A genus 

 of Diatomacese. 



Char. Frustules cuneate, stipitate, di- 

 vided into loculi by transverse septa ; valves 

 obovato-lanceolate, with moniliform vittae 

 in the front view. Marine ; not British. 



C. australis. Very shortly stipitate ; sides 

 of the valves not (very faintly?) striated. 



On Algae from New Holland and South 

 Africa. 



C. moniligera (PL 25. tig. 9). Stipitate, 

 sides of the valves transversely striated (, 

 front view ; 6, side view). 



In the Gulf of Mexico. 



Rabenhorst enumerates 6 species. 



BIBL. Ehrenb. Abh. Berl. Ak. 1841, 401 : 

 id. Ber. 1843 ; Kiitzing, Badllar. 123, and 

 Sp.Alg. 114; Rabenhorst, Alg. i. 299. 



CLIMACOS'TOMUM, Stein, = Spirosto- 

 mum virens, Ehr. 



CLI'ONA, Grant. A genus of marine 

 Sponges. By means of the spicula imbedded 

 in their surface, they burrow into rocks, 

 shells, and stones. 



BIBL. Gosse, Mar. Zool. i. 5 ; Hancock, 

 Ann. Nat. Hist. 1849, i. 321 ; Bowel-bank, 

 Brit. Spog. ii. p. 212. 



CLONOS'TACH YS, Corda. Agenus of 

 Mucedines (Hyphomycetous Fungi), appa- 

 rently not distinct from BOTRYTIS. 



C. araucaria (fig. 347) has been found in 

 England. 



BIBL. Corda, Prachtft. europ. Schimmel- 

 Uld. pi. 15 ; Currey, Qu. Mic. Jn. v. 126. 



CLOSTE'RIUM, Nitzsch. A genus of 

 Desmidiaceae (Confervoid Algae). 



Char. Cells single, elongated, attenuated 

 towards each end, entire ; mostly curved 

 Innately or arcuate ; junction of the seg- 

 ments marked by a pale transverse band. 

 Eudochrome green. 



This beautiful genus is of great interest to 

 the scientific microscopic observer. Many 

 of the species are very common, so that 

 scarcely a drop can be taken from the bot- 

 tom of a clear pool without some of them 

 being contained in it. 



Each cell is composed of two equal por- 

 tions, uniting at a transverse line occupying 

 the middle of the cell. The endochrome 

 exhibits longitudinal bands (PL 14. fig. 40), 



the number varying in different species, of 

 a darker green than the rest of the endo- 

 chrome (PL 14. figs. 40, 41, 43). A num- 

 ber of chlorophyll-vesicles are frequently 

 visible in the endochrome, sometimes scat- 

 tered irregularly, at others arranged in lon- 

 gitudinal series (PL 14. fig. 43) ; at certain 

 periods these contain starch-granules. 



The green endochrome is separated from 

 the cell-wall by a stratum of colourless pro- 

 toplasm which occupies a bluntly triangular 

 space at each extremity. In many cases 

 the protoplasm at these ends exhibits a 

 large roundish vacuole, in which a number 

 of minute granules are contained, often in 

 active motion. Similar granules are visible 

 in the marginal line of protoplasm, which 

 exhibits a distinct circulation, requiring a 

 power of about 400 to show it clearly. 

 Focke, Osborne, and others have described 

 cilia inside the cell-wall, and attributed the 

 circulation to their action ; but this is erro- 

 neous. The protoplasm appears to flow up 

 over the interior of the cell-wall on all 

 sides, from the centre to the extremity, 

 then to turn round past the vacuole, and 

 return over the surface of the green endo- 

 chrome parallel to the upward course. 

 Wills states that the vacuoles at the ends 

 of the cells are contractile vesicles, con- 

 nected with the flow of the currents. 



The Closteria are reproduced in various 

 ways. The individuals divide, like the re&t 

 of the Desmidiaceae, the separation taking 

 place transversely in the situation of the 

 transparent space, where two new half-cells 

 become developed, subsequently separating. 

 As these new ' halves ' are often very small 

 at the epoch of separation, specimens occur 

 with the two portions very unequal. 



Another mode of reproduction is by con- 

 jugation. In this, a pair of individuals be- 

 come united somewhat in the same way as 

 in the Zygnemaceae ; ordinarily the indi- 

 viduals conjugate by the convex side. The 

 process is this : The outer membranes of 

 the parents split circularly in the situation 

 of the central transverse space ; a delicate 

 internal membrane is protruded from each 

 as a sac, and these meet and coalesce. 

 Sometimes the sacs are in pairs from each 

 parent-cell. (See CONJUGATION.) When 

 the cross process is complete, the contents 

 of both parent-cells pass into it and become 

 collected into a globular or squarish cell or 

 zygospore (PL 14. figs. 42 & 46.). Dif- 

 ferent statements are made with regard 

 to the ultimate history of this; and it is 



