STERELMINTHA. 



79 



in oilier forms of the Pulmonigrada occupy a similar position, and 

 at certain seasons of Fig.si. 



the year become re- 

 markably distended 

 with ova ; but, from 

 the observations of 

 these writers, it 

 would seem that the 

 young medusae arc 

 hatched in the ova- 

 ria, and afterwards 

 escape in a very per- 

 fect state of deve- 

 lopement. One of 

 the ovaria of Medusa 

 aurita is represented 

 in the annexed figure, 

 (fig. 81, 1,) taken 

 from Ehrenberg's ela- 

 borate plates of the 



anatomy of this animal, in which a, b indicate the extremities of 

 the convoluted organs in which the germs are developed. The 

 gemmules, when mature, are, according to this author, covered with 

 locomotive cilia like those of sponges and polyps (). 



In Physalus the ova would seem to be generated by the 

 long undulating filaments attached to the lower surface of 

 the body, and in Beroe the ovaria are seen to form clusters 

 around the alimentary canal ; but we are ignorant of the mode 

 of their developement, and of the circumstances connected with 

 the exclusion of the young. 



CHAPTER VI. 



STERELMINTHA. 



Parenchymatous Entozoa. (Cuv.) 



The ENTOZOA, as the name implies, are nourished within the 

 bodies of other animals, from the juices of which they derive their 

 sustenance. It may naturally be supposed that living under such 



