CCELENTERATES. 



23 



each with its peculiarities. Thus in one group the zooids are seated in bell- 

 shaped cups, and since the Latin campanula means a little bell, this group 

 is called Campanularians. The diagram illustrates 

 the history of the group, which is like that de- 

 tailed above. In the reproductive capsule, g, can 

 be seen the young jelly-fishes in various stages of 

 development, while the dotted tissue extending 

 through all parts of the colony indicates the canals 

 by which all are connected, and shows the way in 

 which the food taken by the feeding-forms is able 

 to nourish all parts of the colony. 



Obelia is the musical name of another genus 

 represented in our figures, which show a por- 

 Aifev, tion of a colony, and also a young 



jelly-fish, just as it escapes from 



the reproductive capsule. Specimens 



of Obelia are very common on the 



large sea-weeds known as " devils' 



aprons," the white, root-like portion 



being attached to the frond, and at 



intervals sending up stalks bearing 



the hydroids. The jelly-fish, it will 

 FiG.2i.-Hydroid k e noticed, differs from those already described, in that it is 



stage of Obelia. ** 



a nearly flat disc. 



There are also jelly-fishes which are like those already 

 described, but with the 

 difference that their eggs 

 do not develop hydroid 

 colonies, but give rise to 

 jelly-fish exactly like the parents. 



In an entirely distinct group of 

 jelly-fishes the individuals are much 

 than those we have been de- 

 indeed, some of them are 

 enormous. On our New England coast 

 two of these species are very abun- 

 dant, and at times a strong sea-breeze 

 will drive them in-shore, so that the 

 surfaces of the harbors are absolutely 

 covered by them. The most abundant is the large blue jelly-fish (C, 

 This may well lay claim to the front rank among all the jelly-fishes on 



Fig. 20. — Diagram of a campanu- 

 larian hydroid, showing the feed- 

 ing-zooids(/i), supported on their 

 long stalks, which arise from th" 

 root-like base (r) ; at g is a repro- 

 ductive capsule containing young 

 jelly-rishes(r/i';, while at m is one 

 which has escaped. The dotted 

 portions of the figure show the 

 way in which all the zooids are 

 connected. 



has the tentacles 

 expanded, while 

 farther down on 

 the stalk is a re- 

 productive cap- 

 sule, from which 

 the young jelly- 

 fishes (Fig. 22) 

 are soon to es- 

 cape. 



larger 

 scribing ; 



Fig. 22. — Jelly-fish of Obelia, greatly enlarged. 



