450 ORDER CILIO-FLAGELLATA. 



transverse groove projecting, and presenting laterally the aspect of tooth- 

 like processes ; facets developed on each side of equatorial furrow, five in 

 number. Diameter 1-1152" to 1-480". 



HAB. Salt water : Naples. Highly phosphorescent. 



In contour this species would appear to closely resemble the smooth variety of 

 the fresh-water Peridinium tabulatum. 



Peridinium chilophsenum, Ehr. 



Cuirass subglobose, hornless, its surface smooth, neither facetted nor 

 punctate ; equatorial furrow distinct, its margins presenting laterally the 

 appearance of projecting teeth ; oral fossa narrow, curved. Diameter 

 1-648". 



HAB. Salt water : entrance of Davis Straits, and Iceland, with sound- 

 ings from a depth of 1158 feet. 



Peridinium sanguineum, Carter. 



Body subcircular, paraboloidal or kite-shaped, compressed, sulcate 

 ventrally ; equatorial groove deep, its upper border distinctly ciliate ; cuirass 

 faintly facetted over the anterior or conical half, the posterior or rounded 

 half entirely smooth ; an eye-like pigment-spot and endoplast usually 

 conspicuous. Length i-H2o"to 1-700". 



HAB. Salt-water pools, and in the sea on the shores of the Island of 

 Bombay. Movements waddling, the small end forwards and the long 

 flagellum floating behind ; colour changing successively from green or 

 golden yellow to brown and vermilion or minium red. 



This species, described by Mr. H. J. Carter in an article on " The Red Colouring 

 Matter of the Sea round the Shores of the Island of Bombay," contributed to the 

 ' Annals of Natural History ' for April 1858, is of special interest in connection with 

 the light it throws upon the phenomena frequently observed, but not previously 

 explained in a satisfactory manner, concerning the sudden assumption by the sea, or 

 other waters, of a blood-red hue. According to Mr. Carter, this animalcule, during 

 the earlier and active phase of its existence, is green and translucent, reflecting little 

 or no light, the colouring matter out of which its body-substance is composed being 

 akin to or identical with the chlorophyll of plants. Gradually, as the time approaches 

 for it to assume its quiescent or encysted state, a number of semi-translucent, refrac- 

 tive oil-globules are secreted within the interior ; the green colour now disappears 

 and a bright red one takes its place, mixing with the oil, and thus the animalcules 

 become visible to the naked eye, the whole portion of the sea charged with them 

 acquiring a deep vermilion hue. This colour is so prominently developed under 

 these conditions that in the sea-water pools left by the reflux of the tide on the 

 shores of the Island of Bombay, such pools present to the uninitiated the appearance 

 of having had a quantity of vermilion or minium thrown into them. An examina- 

 tion of this water under a microscope shows, however, that the red colours are 

 entirely due to the Peridinia. The vermilion hue now arrived at only lasts a few 

 days ; the animalcules assembling together become individually encapsuled, and in 

 this state float on the surface or sink to the bottom. Duplicative subdivision now 

 takes place within the capsules or encystments, each animalcule by such process 

 becoming divided into two or four equal fragments, which are subsequently 

 liberated by the bursting of the cyst. In other, rarer instances, it is affirmed by Mr. 

 Carter that a litter of ciliated monads may be developed in a distinct cell within the 



