184 



LECTURE IX. 



With regard to the marsupial sacs on the arms of CycmcBa aurita, 

 these are attached to the fringed processes on each side of the oral 



3. Gemmation of 



Hydra tuba. 



89. Scyphistoma. 



92 



Spontaneous fission of Strobila. 



Ephyra. 



arms. They are developed before the ova quit the ovaria; are 

 largest on the upper and middle part of the arms, while at the under- 

 most part only small and usually empty sacs are found. Do they 

 disappear after the progeny is developed and the breeding season 

 past, or does the parent perish with them when her maternal and 

 nutricial functions have been performed ? The membrane from which 

 the sacs are developed is beset on its free edge, both in males and 

 females, with numerous tentacles, similar to those found in the gene- 

 rative or respiratory cavities. Siebold thinks they are more numerous 

 in the male than the female. 



The subsequent metamorphoses, or rather metageneses, of the 

 larval medusae are equally extraordinary with those above described, 

 which the observations of Siebold have mainly contributed to explain. 

 The cycle of these changes is so remarkable, that I feel bound to 

 submit the whole body of evidence, from different and independent 

 witnesses, by which the phenomena have been established and linked 

 together. 



It is now sixty years since Otho Fred. Miiller first described and 

 fif^ured* a marine Polype, which, from its general resemblance to the 

 fresh- water kind, he called Hydra gelatinosa : it is the Hydra tuba, 

 of Daly ell, or a larval Medusa at the same polypoid stage. 



Eschcholtz, in 1829 f, first described a small medusoid animal 

 which he called Ephyra ; this now turns out to be the penultimate 

 ^tage of Cyancea aurita. 



* CLIV. vol. iii. p. 25. t. xcv. 



t CLV. 



