NARRATIVE OF THE CRUISE. 
935 
Pyrocystis noctiluca. — Mr. Murray says : — “ This organism is always present, and 
often in enormous abundance, at the surface of the open ocean in tropical and subtropical 
that forms phylogenetically closely allied may live some as plants others - as animals. He proposes the theory that the 
Flagellata are a primitive group from which the Noctilucidse, Rhizopoda, and Cilio-flagellata are derived, and that from 
the last come the Peritricha, and from these the other Ciliata. 
“ Since the appearance of this paper, George Klebs* in 1883 published some observations on the freshwater forms, 
and more recently has given an account of the marine Peridiniidse.t 
“Claparbde and Lachmann considered Cilio-flagellata, as unicellular animals, intermediate between Ciliata and 
Flagellata. Warming, J however, in 1875, expressed the opinion that the Peridiniidse were plants and ought to be 
classified as intermediate between the Diatoms and Desmids. Nearly all observers, including Prof. Allman, agree in 
ascribing to them a long flagellum and a row or two rows of cilia in the equatorial groove. There seems to be some 
reason to doubt the existence of the equatorial cilia, at least in some species. Polykrilcos auricularia, Biitschli, certainly 
possesses eight rows of cilia, but according to Klebs it is a true ciliate Infusorian and not a Peridinean at all. As to the 
existence of the posterior flagellum in Cemtium there is no doubt, though often it cannot be observed ; it arises from the 
protoplasm of the body within the aperture of the case, and I have myself seen it in active motion. I have not been able 
to detect any cilia, and Klebs up till a short time ago had been unable to discover any locomotive organ except a single 
flagellum. In the account of his recent studies of the marine Peridiniidae, Klebs makes the following statements con- 
cerning the locomotive organs. Upon the long flagellum which projects backwards in Ceratium he has nothing new to 
communicate ; it is as described by earlier writers. But several times he observed in Ceratium tripos a second flagellum, 
arising like the first from the ventral longitudinal cleft, and he believes that in the normal condition this second 
flagellum vibrates in the equatorial furrow, like the furrow-flagellum which he observed in freshwater forms. He has 
not been able to find the opening by means of which the flagella and internal protoplasm are continuous. With regard 
to this point I see no difficulty ; in my own observation referred to above, although I could not make out the actual 
junction of the flagellum with the protoplasm, it was perfectly obvious that the flagellum arose within the area on the 
ventral surface of the body where the protoplasm was nude. As described and figured by Bergh, the case is wanting over 
this area and the protoplasm is uncovered. Klebs also says that he has never seen a specimen of Ceratium tripos in loco- 
motion. The-specimen which I was able to observe at my leisure for some time moved across the field of the microscope 
with considerable rapidity, so that I had some difficulty in keeping it in view until I fixed it by means of a cover-glass. 
“Concerning the internal organisation, Klebs extends what he said of freshwater forms to those of the sea. 
Usually the protoplasm is coloured yellow by diatomin, which is not diffused but confined to definite bodies like 
chlorophyll corpuscles. He also found starch and colourless oil in the cytoplasm. He observed a process in Ceratium 
fusus which seemed like spore formation. Copulation he had never seen. The chain forms, observed first by Mr. 
Murray and afterwards by Pouchet, he regards as connected with a pelagic mode of life ; this I do not understand ; 
chains of pelagic organisms such as Diatoms, Salpa, &c., are produced by budding or division, and therefore the same is 
probably the case in Ceratium tripos. 
“ Physiologically the species of Ceratium are certainly plants. The substance of which the case consists is closely 
allied to cellulose, and contains no inorganic matter ; unlike cellulose, it is not dissolved by ammoniacal oxide of 
copper. The body contains a single oval nucleus, deeply stained by the action of carmine. 
“ Although some Flagellata undoubtedly live as animals, it has not yet been absolutely proved that any of the 
Peridiniidae digest. Stein and Bergh affirm the fact in Gymnodinium, but Klebs does not accept their conclusion. 
“Unless the occurrence of Ceratium tripos in chains be due to a process of division, nothing is known of the 
multiplication or reproduction of Ceratium. In allied freshwater forms division has been known to occur for some 
time. In Peridinium tabulatum and Glenodinium cinctum, according to Klebs, the old case is burst during division into 
two halves at the transverse furrow and thrown off, each of the new cells forming a new case for itself. 
“ Klebs decided from his studies of freshwater forms, that the Peridiniidse were a group of unicellular plants to 
be classed with the Thallophytes, their immediate affinities being uncertain. From his study of the marine forms he 
comes to the conclusion that Exuvicella marina, Cienkowski, is a true Peridinean, and that this organism shows 
affinities on the one hand with the yellow cells of Radiolarians, on the other with the Cryptomonads, the central group 
of the Flagellata. 
“ Ceratium may be therefore considered as a genus of unicellular Algae. Three species of Ceratium ( Ceratium tripos, 
Ceratium furca, and Ceratium fusus ) are extremely abundant in the waters of the Firth of Forth and neighbouring seas 
at all seasons.” 
* Untersucliungen aus dein botanisclien Institut m Tubingen, Bd. i. p. 346, 1883. 
| Botanische Zeitung, Nos. 46 and 47, 1884. 
J Vidensk. Meddel. f. d. nat. Foren. i Kj.fbenha.vn, Aaret 1875. 
(narr. chall. exp.— wol. i. — 1885.) 
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