GENUS PERIDINIUM. 



451 



oi'dinary capsule, such brood being the product of a true act of generation (con- 

 jugation), or the final formative effort of the protoplasm. 



Many earlier records of the observation of phenomena connected probably with 

 the presence of an animalcule identical with, or alhed to, Pcridiniuin sangtiincum are 

 quoted by Mr. Carter. Thus, Charles Darwin * observed an apparently identical 

 animalcule which coloured the sea red, a degree south of Valparaiso. Salt in 

 his ' Voyage to Abyssinia,' mentions the presence of animalcules in the Red Sea, 

 which produced the red colour characteristic of those waters during the day, and 

 became luminous at night by agitation after the manner of numerous other Pcridinia. 

 Olafsen and Povelsen are further cited as having recorded, so long since as 1694, of 

 the sea on the shores of Iceland, that during the daytime it was as red as blood, and in 

 the night apparently as though on fire. Mr. Carter finally suggests the high probability 

 that the plague of Egypt — manifested by the apparent turning of all the waters into 

 blood, in which the fish in the river died, and the river stank, and the Egyptians 

 could not drink of the water of the river — may be consistently interpreted in con- 

 nection with an abnormal development of an animalcule allied to this species. 

 Such interpretation is further supported by facts connected with the discoloration 

 of the sea, that Dr. Buist recorded in the ' Proceedings of the Bombay Geological 

 Society' for the year 1855. On the 27th of October 1849 it was observed by that 

 authority that the water at Ponbunder, on the coast of Khattywar, was changed from 

 the usual tint to a deep red, emitting a most foul smell ; the fish weie speedily all 

 destroyed, and were washed upon the beach in large quantities. It was conjectured 

 by the narrator that the phenomenon was owing to some submarine eruption of mud, 

 but the locality being one in which red water produced by the presence of animal- 

 cules is extremely common, the cataclysmic interpretation suggested is scarcely 

 warranted. The offensive effluvium exhaled by waters in which Feridinia and 

 lower Protophytes have developed in large quantities is personally testified to by 

 Mr. Carter in the case of a Peridinmm obtained by him from a fresh-water tank at 

 Bombay, and where he says it not only " turned the water quite brown, but imparted 

 a smell and insipid taste to it, which almost rendered it undrinkable." He further 

 cites the case of a little algal, Aphanizomenon flos-aquce, frequently developed under 

 like conditions in the same fresh-water tanks, which often not only "renders the 

 water undrinkable, but produces an intolerable stench by its putrefaction." 



It may be suitably mentioned in connection with the foregoing data that 

 Ehrenberg, in the ' Monatsbericht der Berliner Akademie ' for the year 1853, 

 records the fact that during the remarkable cholera epidemic prevalent throughout 

 Europe in the year 1848, two flagellate organisms, Chloraster gyrans and Spondylo- 

 mornm giiafernarium, were so abundandy developed in the water-tanks in the streets 

 of Berlin as to render the fluid completely green and unfit to drink. If not the 

 direct cause of zymotic disease, there can be but little doubt that an abnormal 

 development of these and kindred lowly organized beings in ordinarily potable 

 water indicates that such fluid has been contaminated by the accession of extraneously 

 derived organic matter to an extent making it not only unsuitable, but highly 

 deleterious for human consumption. 



Peridinmm sequalis, S. K. Pl. XXV. Fig, 14. 



Body symmetrically bi-conoidal, widest in the centre, tapering evenly 

 at an angle of about 6'j'^ towards the anterior and posterior extremities, 

 both of which terminate in two or more short, pointed cusps ; equatorial 

 zone of cilia broad and evenly developed ; a second furrow of equal breadth 

 proceeding from the centre of the equatorial one towards the anterior pole ; 

 measurement between the two poles scarcely exceeding that of the width ; 

 endoplast conspicuous, band-like. Dimensions unrecorded. 



Hab. — Salt-water. 



* 'Journal on board H.M.S. Beagle,^ pp. 17, 18. 



2 G 2 



