372 



NATURAL HISTORY. 



charon the dorsal surface of the body is ribbed, as it were, and there are seven frontal and three 

 ventral styles, besides five posterior strong setre (Fig. 34). 



ORDER CILIO-FLAGELLATA. 



The animalcules of this order are readily distinguished by their bodies being more or less 

 ciliated, and by their having a long lash-like flagellum. The mouth is usually distinct. Saville Kent 

 divides them into four families and sixteen genera, and the individuals are occasionally very numerous, 

 producing the phosphorescent condition of the sea, and discolouring fresh and salt water. Most of 

 the Cilio-flagellata, a type of which has already been noticed (pp. 356-7), are small, -g^th of an inch 

 being the greatest length, but amongst the genus Ceratium there are some large forms, some reaching 

 Y^th of an inch in length. They are found in fresh and in salt water ; and, so far as is known, none 

 are parasitic or sedentary ; but during one of the reproductive phases encystment occurs, and a 

 period of quiescence precedes the escape of the young. They are active swimmers as a rule, the 

 lash-like flagellum (in rare instances there are two) enabling rapid and irregular motion easy, and 

 the cilia produce ordinary movement. Fission occurs, but the reproductive phenomena have not 

 been observed satisfactorily. Some of the Cilio-flagellata are naked, and others have a shell, or 

 horny cuirass, which may be smooth or ornamented, and often prolonged into horn-like processes. 

 Some of these loricse have been preserved in the strata of the chalk, and are referred to the genus 

 Ceratium. The general character of the group having been given already, it is only necessary to 

 observe that the family Peridinidse contains ten genera. In all there is a distinct ciliary girdle, and 

 one flagellum. In a doubtful genus there are two of these organs. In some of the genera the ciliary 

 girdle is central, in others eccentric, and in one it is terminal. Some genera have a cuirass, and many 

 others are naked. Melodinium, already noticed (p. 356), is an example of a naked, and Ceratium 

 of a cuirassed and honied genus. Peridinium has no horn-like processes, and the cuirass is facetted 



(Fig. 4, A-H). 



The second family* has one vibratile flagellum, and one which is trailed, and the body changes 

 in shape, like Amoeba ; and the third familyt has the body clothed with long setose cilia, and a 

 terminal flagellum, the body shape being persistent. A fourth family has a wreath-like crest or 

 collar of cilia, and in the midst a flagellum, which may or may not be retractile ; J and the last 

 family, which links the order with that of the Ciliata, has a more or less perfect ciliary covering, 

 and a flagellum. The colours differ, and there may or may not be a red spot in these families. 

 Yellow, light-brown, green, pink, reddish-brown, vermilion, are common colours ; and usually the 

 endoplasm is transparent, and holds coloured matters in suspension. Peridinium splendor-marls 

 of Naples is highly phosphorescent, and P. sanguineum, of salt-water pools and the sea-shore of 

 India, is green when young, and with growth a number of oil globules is secreted within, and the 

 green colour disappears, and a bright red tint comes on, just before encystment. The red colour of 



patches of the sea is due to this form, in many 

 instances, and it is noteworthy that the 

 presence of these animalcules renders water 

 c ^ .x-k. very disagreeable. 



Fig. 35. MONAS DALLIXGERI. (Saville Kent. ) 



A, B, Adult : c, about to encyst; D, K, p, eneystment formation of spores which 

 are liberated as monads; G, H, conjugation : i, cnrygtment from conjugation; 

 j, bursting of and liberation of spores ismall). 



ORDER FLAGELLATA. 



These animalcules, generally very minute, 

 have one or more long slender flagella ; there 

 are in some instances pseudopodia. The 

 mouth may be doubtfully present, and food 

 may be taken in at one' spot, or anywhere. 

 One or more contractile vesicles are almost invariably present. They increase by fission, or In- 

 breaking up of the endoplasm in the encysted state. 



This definition explains how difficult it is to limit the lower Flagellata. It is possible that many 

 of the so-called Flagellata are stages of plants, and indeed it seems impossible to draw a hard and 



* ffeteromastigidce (Fig. 4, K). t MaUomonadidce (Fig. 4, L). J Stephanomonadidai (Fig. 4, i). 



Trickoncmidcc (Fig. 4, j). 



