THE DISCOPHORES, OR LARGE MEDUSiE. 
127 
that in the course of a short season the minute slice of the 
polypite has attained the extraordinary size and complexity of 
the gigantic Cyancea , before referred to. All their energies 
are devoted to the nutrition, protection, and dispersion of the 
embryos ; and having accomplished this work, they probably 
fade and perish. They share the beauty, and the frailty and 
transiency of the flower. 
I shall now gather together some interesting particulars of 
their habits and mode of life. Born in the spring, they swarm 
at this season in immense numbers near the shore ; as the 
summer advances, and they increase in size, they seem to 
disperse themselves over the surface of the ocean, congregating 
again in autumn for the purpose of spawning. In warm, 
serene weather they keep near the surface, and “ wander in 
the luxury of light ; ” in storms they sink to the safer 
depths. Their numbers are simply incalculable ; off our own 
coasts they may be seen in immense shoals. Sailing from 
Holyhead on a fine evening, I have seen the water of the 
harbour so densely packed with them that the steamer almost 
seemed to be cleaving its way through a solid mass. The works 
of voyagers and travellers are full of marvellous accounts of 
the crowds of Medusae which they have encountered. Lesson 
tells us that off the coast of Peru he met with millions of 
individuals of a certain species, pressing closely one against the 
other as they moved along, and all having the disc directed 
towards the north ; the sea was perfectly calm. Dr. Colling- 
wood describes a shoal in the Atlantic. “ Just before sunset,” 
he writes, “ we passed through them for a space of two hours, 
during which time we had traversed ten miles. It was easy to 
calculate roughly that there could not be less than thirty 
millions of individuals constituting the shoal — an estimate 
probably far below the mark.” We shall hardly be surprised at 
their numbers, if we bear in mind the facts of their history. 
Each polypite, by budding, multiplies itself to an amazing 
extent, and so provides a large family, each one of which will 
in due time produce its complement of Medusae ; and, further, 
each one of the second generation multiplies in the same way, 
and each one of many successive generations, before the 
development of the Medusa-brood sets in. And of this vast 
company, the ultimate product of a single zooid, e^ch one that 
survives may originate a dozen Medusae or more. Of such 
myriads no census can be taken. 
In autumn the Medusan tribes return from their oceanic 
wanderings, and congregate near the shore. Massed together 
in enormous shoals they discharge the embryos, which it has 
been their function to mature, in the neighbourhood of the 
littoral region in which they are to find a home. Agassiz has 
