14 OCEAN LIFE. 



is seen swollen out into separate ovate sacks, ten or more in num- 

 ber, each of which contains several embryos. Those nearest the 

 mouth of the vesicle are first developed, and escape successively 

 by slowly emerging from the pitcher-like rim." This little 

 medusa-like creature, freed from its parent cell, has the power 

 of moving about rapidly in all directions through the water. 



Mr. Peach, who first observed them, says : " They resemble 

 umbrellas without handles, or very wide and short hand bells." 

 He also remarks : " They assume various positions, and, when 

 in the water, remind me of thousands of parachutes thrown from 

 a balloon, descending in various states of expansion." The phe- 

 nomena of which we have spoken, strikingly illustrate the law 

 known as " the alternation of generations," and may be briefly 

 summed up as follows : " The Polype, a fixed and rooted ani- 

 mal, increases its own individual life for awhile, by putting forth 

 a succession of budding heads, but at a certain period gives birth 

 to a number of beings that bear no resemblance to itself in form 

 or habit, but are, to all intents and purposes, free, swimming 

 medusae. Each of these, after pursuing its giddy course for a 

 time, produces a number of eggs, which change into active ani- 

 mals, having the closest resemblance to infusoria. Each of these 

 latter presently becomes stationary, and affixed to some foreign 

 body, along which it creeps as a root thread, shooting up tubular 

 and celled Polypes. 



" Hence, any one individual is not at all like its mother or its 

 daughter, but exactly resembles its grandmother or its grand- 

 daughter." In other words, the alternations are as follows: 

 1. The medusa produces eggs. 2. The eggs, after passing through 

 an infusorial state, become Polypes, like Corynae, Tubulariae, or 

 Campanulariae. 3. The Polype produces a kind of bud that 

 finally drops off and becomes a medusa. Thus, the egg of a Me- 

 dusa, in such cases, does not produce a Medusa except after going 

 through the intermediate state of the Polype. Or, if we com- 

 mence with the Polype, the series is : 1. The Polype produces 

 bulbs that become Medusae. 2. The Medusae produce eggs. 

 3. The eggs produce Polypes. 



