t>esmulie(P.'\ iivFrsoRiAL animalcules. 283 



beaks, -vrhicli are shorter than the ventricose body. Vesicles dis- 

 posed rather ii-reguhirly in a single row ; fillets generally obscure ; 

 empty frond reddish. Length l-79th. 



Closterifm rostratum (Ehi'.) — Closely striated, tapering at each 

 end into a setaceous curved beak, which is about eipial in length to 

 the ventricose body. Fillets obscure ; vesicles in a single row. 

 Empty ft'ond coloiuicss or straw coloured. Length l-69th. 



C. setaceiim (Ehi*.) — Very slender, finely sti'iated, narrow lanceo- 

 ate, tapering at each extremity into a very long setaceous beak, 

 which alone is curved ; vesicles none or obscure. Fillets none. 

 Sporangium quadi'ate or cruciform (P. 1. f. 67.) Length 1-1 16th. 



Ehrenberg discovered this species in May, 1832 ; and, in 1835, ob- 

 served the process of copulation (conjugation.) On the issuing forth 

 of the green matter separation took place into four instead of two 

 portions, and the green matter formed itself into a flat eight-cornered 

 body, with a bright spot in its centre, and granular contents. (See 

 figau'e on right side of group 67, Plate 1.) 



f f Frond minute, tapeiing, not rostrate ; empty fi'ond colomioss 

 and Avithout markings. 



C. cornu (Ehi-.) — Smooth, minute, curved, very slender; extremi- 

 ties slightly attenuated ; ends obtuse ; vesicles none or indistinct ; 

 sporangium quadrate. 



Var. fh.J — Frond more turgid. Length 1-1 40th. Length of 

 var. fbj 1 -226th. 



C. acutum.. — Curved, gradually tapering at each extremitj^ ; ends 

 more or less acute ; empty fi'oud colourless, without markings. 



Var. fa. J — Six to twelve times longer than broad; vesicles ob- 

 scure ; fillets none ; ends sub- acute. 



Var. fb.J — Ten to twenty times longer than broad, tapering at each 

 extremity into a very fine point. Length 1-1 77th. 



C. cuspidatum (Bailey.) — Smooth, crescent-shaped ; ends murro- 

 nate. It differs from every other species of the genus in having 

 each end tipped by a spine or mucro- 



C. cucumis (Ehr.) — Smooth, stout, semilunate ; ends broadly 

 rounded. In form it resembles C lunula, but is stouter in proportion 

 to its length, and has its ends more rounded. 



C. Tliurcti. — Smooth, crescent-shaped ; ends sub-acute ; margina 

 unconnected at the suture ; vesicles in a single series 



c 2 



