. Cassell's natural history. Animals; Animal behavior. 372 NATUliAL HlfSTORY. charon tlie tlorsa'i surface of the body is ribbed, as it were, and there are seven frontal and tliree ventral styles, besides live posterior strong seta3 (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 condit
. Cassell's natural history. Animals; Animal behavior. 372 NATUliAL HlfSTORY. charon tlie tlorsa'i surface of the body is ribbed, as it were, and there are seven frontal and tliree ventral styles, besides live posterior strong seta3 (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 CiUo-flagellata, a type of which has already been noticed (pp. 356-7), are small, -~j^t\\ of an inch being the greatest length, but amongst the genus Ceratium there are some large forms, some reaching yj 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 sedentaiy ; 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 loricEe 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 Peridinidie 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 excentric, and in one i
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