88 DISCOPHOR^. Part III. 



in accordance -with a foncied similarity, but by no means in consequence of a 

 careful comparison. And, if some of these appellations are still used by modern 

 zoologists, it is hardly because they acknowledge a real resemblance between them, 

 but rather to avoid useless innovations. The time has come, however, when such 

 apprehensions should no longer prevent us from a critical comparison, and if the 

 result should show essential differences between all the parts Avhich bear names 

 otherwise in use to designate characteristic parts of other animals, then the dread 

 of a large increase of technical terms ought to be superseded by the hope that 

 the changes may be for the real advantage of science. 



Let us take a general survey of the curious animal to which this chapter is 

 devoted. Seen floating in the water it exhibits a large circular disk, of a substance 

 not unlike jelly, thick in the centre, and suddenly thinning out towards the edge, 

 which presents several indentations. The centre of that disk is of a dark purj^lish- 

 brown color, while the edge is much lighter, almost white and transparent. This 

 disk is constantly heaving and falling, at regular intervals; the margin is especially 

 active, so much so, that, at times, it is stretched on a level with the whole surface 

 of the disk, Avhich, in such a condition, is almost flat, while, at other times, it is so 

 fully arched that it assumes the appearance of a hemisphere. These motions 

 recall so strongly those of an umbrella, alternately opened and shut, that Avriters, 

 who have described similar animals, have generally called this gelatinous disk the 

 umbrella.^ From the lower surface of this disk hang, conspicuously, three kinds of 

 appendages. Near the margin there are eight bunches of long tentacles, moving in 

 every direction, sometimes extending to an enormous length, sometimes shortened 

 to a mere coil of entangled threads, constantly rising and falling, stretching now 

 in one direction and then in another, but generally spreading slantingly in a direction 

 opposite to that of the onward movement of the animal. These streamers may 

 be compared to floating tresses of hair, encircling organs which are farther inward 

 upon the lower surfiice of the disk. Of these organs, there are also eight bunches, 

 which alternate with the eight bunches of tentacles, but they are of two kinds; 

 four are elegant sacks, adorned, as it were, with waving ruffles projecting in large 

 clusters, which are alternately pressed forward and withdrawn, and might also be 

 compared to bunches of grapes, by turns inflated and collajDsed. These four bunches 



' Tlie name of umbrella, for the gelatinous disk would no longer be appropriate. I need only re- 



of all Discophorous Medusa*, is so characteristic, that mind the reader of the globular form of Pleuro- 



I would unhesitatingly have retained it to desig- brachia, or of the cylindrical form of Idyia, or of 



nate that part of the body of an Acaleph, were the winged Bolina, or of the polygonal form of many 



there not many members of the class in which it compound Siphonophora;, and, perhaps still more, 



assumes forms so entirely different from the flat, of the club-shaped Hydroids, and of the young Dis- 



bell-shaped outline it exhibits here, that the simile cophoriE. 



