24 



NATURAL HISTORY. 



account of its size. Mr. Agassiz says that one which he saw had a disc 

 seven feet and a half in diameter, and tentacles streaming behind to the 

 distance of one hundred and twenty feet. Even larger individuals occur 

 the disc occasionally measuring ten feet in diameter. When alive their 

 color is a dirty reddish brown, which after death changes to light blue, 

 whence both the common and scientific names. When we consider this 

 and the next species, the appropriateness of the common name "jelly- 

 fish " is at once apparent, for in consistency they closely resemble wine 

 jelly. The broad frills and the long tentacles which hang down from 

 the disc have a little more consistency, and it is on these that the nettle- 

 cells occur which give this species its unenviable reputation mentioned 

 on a preceding page. 



Our other common species is Aiirelia, a form creamy white in color, 

 and without the long tentacles so characteristic of Cijanea. Both this and 

 the last species swim lazily through the water by slow yet forcible con- 

 tractions of their discs. The young Cijanea, which is figured (Fig. 25), is 

 but rarely seen by naturalists, possibly from the fact that its habits do not 

 correspond with those of man. Mr. Alexander Agassiz writes, " Having 

 accidentally visited the wharves of Provincetown harbor early one morn- 

 ing, between four and five, I was astonished to perceive what a large 

 number of young Cyanea3 were floating about, measuring all the way from 

 a- quarter of an inch to three inches in diameter. On my return to the 

 same place at seven o'clock, although not a breath of air had ruffled 

 the surface, they had all returned to deeper water." 



Both the sun-jelly and the blue-jelly pass through an alternation of 

 generations considerably different from" that 

 described above. From the egg there hatches 

 out a young animal which swims freely for a 

 short time, and then becomes attached to 

 some submarine object, when it begins to 

 m grow into a form much like a hydra, but with 

 shorter tentacles. This form can eat, and 

 the big s..„- with growth it soon begins to divide trans- 



jelly, Aureha. -. . ° 



versely into a series of discs. Our figure shows 

 the stage of this division at the time when three of the 

 discs have been formed, while below them is a long undi- 

 vided portion of the stock. As the process goes on, the 

 discs, become thinner, flatter, and very numerous, so that 

 the whole resembles in miniature a pile of saucers on the 

 shelves of a china-closet. One by one the discs detach 



Fig. 23. — Hy 

 droid (Scyphis- 

 toma) stage of 



themselves and float away, each one becomin 



<? a 



young 



Fig. 24. — Strobila 

 stage of Aurelia, 

 showing a few of 

 the saucers into 

 which it divides. 

 In later stages the 

 whole stem be- 

 comes divided into 

 a large number of 

 saucers. 



