THE MEDUSA. 13 



The Swedish natiu'alist, M. Sars, was the first who, by 

 his observations and researches, gradually removed the 

 obscmity which veiled the propagation and development 

 of the Medusa. No doubt had been entertained of this 

 being quite simple, that is to say, that it was not only 

 subjected to the general laws of development, but that 

 it was closely connected with the usual phenomena by 

 which those laws are attended. The development of two 

 species of Medicsce — as it has been made known to us by 

 this observer, and as it has been confirmed in certain of 

 its stages by the observations of others, and especially 

 with regard to its first stage by the important observa- 

 tions of Siebold — presents highly remarkable phenomena, 

 which may truly be called peculiar, although they are not 

 fundamentally isolated. It is my direct object in the 

 following pages to endeavom^ to render this clear, and I 

 shall proceed, with all brevity, to make the reader 

 acquainted vdth this course of development, and select 

 as an example that of the Medusa aurita. 



The full-grown Medusce which are met with in summer 

 and autumn are not hermaphrodite, as was formerly be- 

 lieved, but of distinct sexes ; some, consequently, are 

 male and others female. The external form indeed of the 

 generative organs is the same in all, but their internal 

 structm-e and their object are entirely different, and it is 

 simply from the similarity in the outer form of these 

 organs that the erroneous notion has arisen, that herma- 

 phroditism exists not only in this, but in many other fami- 

 hes also. In the globular ova, while still in the ovaries, 

 young are developed, of an oval or cylindrico-oval form, 

 which, at a later period and after they have quitted the 

 egg, are collected into special receptacles, formed at the 

 same time in the four oval tentacles. In these recepta- 

 cles they remain for some time, for the purpose of being, 

 as it were, hatched in them, when they forsake the parent 

 and swim about in the water, as a swarm of distinct 

 creatures. 



At this time they appear slightly compressed laterally, 



