52 CLASSIFICATION OF THE ANIMAL KINGDOM. 



shape according to circumstances. The shells of the loricated gentlemen 

 of course confine their owners within due hounds, but their mailed coats 

 are often beautifully varied in form. Their means of locomotion differ in 

 different species; some move by filaments attached to the body; some are 

 provided with styli, or stiff articulated bristles, which are moveable, and 

 uncini, or little hooks, by which they attach themselves to foreign bodies; 

 others are covered all over with cilia, which vibrate very rapidly; while 

 some have the same organs only round the mouth. The oral orifices of 

 the Polygastrica are usually simple, yet Ehrenberg in some species has 

 described a sort of dental system. Their digestive apparatus consists of a 

 number of internal sacculi, or little stomachs, and in most species there 

 is only one orifice, the mouth, though some more organized pass their 

 food right through the body. Their reproduction is either by external 

 gemmules or buds, or by the same gemmules produced internally, which 

 latter, when ready to come forth, escape by bursting open their common 

 parent; they are also produced by spontaneous division of the body, each 

 part becoming a separate animal. No circulation, or means of respiration, 

 properly so called, has been seen in the Polygastrica, neither has any 

 nervous matter as yet been discovered. 



Next in order comes the class Acalephte, better known by the name 

 of Jelly-fishes. These the author of the book above mentioned, following 

 previous writers, classifies according to their organs of locomotion, and we 

 have the Pulmonigrada, Ciliograda, Physograda, Cirrigrada, and Diphyda. 

 The means of motion in the first order is by the alternate contraction 

 and expansion of the large mushroom-shaped disc comprising the body of 

 the animal, which resembles somewhat the motions of lungs in respiration; 

 from the under surface of this disc hang various elongate processes, an- 

 swering the purposes of tentacula. In the Ciliograda the organs of motion 

 are bands of cilia placed in various parts round the body. The Physograda 

 swim by means of bladders, which the animals inflate at their pleasure. 

 The Cirrigrada move by means of numerous appendages called cirri, which 

 perform the office of oars; these animals possess an internal porous skeleton; 

 while the last, the Diphyda, are very extraordinary creatures, and derive 

 their name from their appearing each one to consist of two separate portions 

 joined together in the slightest way. The whole family possesses but a 

 single cavity or stomach, appropriated to the purposes of digestion, circu- 

 lation, and respiration, which functions are carried on by means of canals, 

 which vary somewhat in different species. Many of them possess the power 

 of stinging, but in what way it is produced seems still to be a mystery. 

 Some have also the property of emitting phosphorescent light, which is 

 exceedingly brilliant in some seas, "many of the larger ones being described 

 by navigators as resembling white hot shot, visible at some depth beneath 



