REPRODUCTION. 147 



a. Sexual Reprodudion — Generation. 



Comparison of the Sexes in the Hi/droida. — The existence of differentiated sex in the 

 Hydroida was first announced by Ehrenberg,' who cnaintained that the so-called "tgg-capsules" 

 in Cori/ne, Sertularia, &c., had the significance of special fertile animals, to which he gave the 

 name of females, while he regarded the ordinary hydranths as the sterile individuals of the 

 colony. 



With this announcement we may date a well-marked era in the history of progressive 

 discovery among the Hydroida ; for it is to the happy conception of Ehrenberg that we must 

 refer the more jihilosophic views which within the last few years have so greatly advanced our 

 knowledge of the structure, functions, and relations of these animals. 



The celebrated German micrologist, however, did not grasp the full meaning of the facts of 

 which he had thus so nearly given us the exact interpretation ; for he regarded the central 

 column (blastostyle) of the gonanginm in Sertularia as the equivalent of the central diverticulum 

 (spadix) in the gonophore of Coryne, while he viewed the gonophores borne on the sides of the 

 blastostyle in Sertularia as merely eggs equivalent to the true eggs contained in the gonophore of 

 Coryne. 



The doctrine of the sexual differentiation of the Hydroida was confirmed by Loven in a 

 remarkable memoir, originally published in the ' Transactions of the Royal Swedish Academy' for 

 1835, and thence translated into Wiegmann's 'Archiv.'- In this memoir Loven gives an account 

 of those singular extracapsular medusiform gonophores which are described above (p. 57) 

 under the name of "meconidia;" he found them in a Campanularian hydroid (Gonotl/yrea 

 Loveni, Allm.), and recognised in them their true sexual function. He also describes the occur- 

 rence of medusi-form gonophores in two species of Syncoryne ; and having observed that in 

 the gonophores of one of these species the cavity of the umbrella was filled with ova, he dis- 

 tinguishes them from mere organs, and regards the gonophores in both instances as special female 

 animals.' 



Naturalists had now not only become familiar with the presence of true ova in the 

 Hydroida, but they saw in the portions of the colony set aside for their production something 

 more than mere organs. No one, however, had as yet discovered any trace of spermatozoa ; 

 Ehrenberg at this time makes no mention of a male element, while Loven calls the nutritive poly- 

 pites male, and in this view of their nature falls behind Ehrenberg, who more truly names them 

 sterile or sexless individuals. 



' ' Corallentliiere, Abhandl. der Kiinigl. Akad. der Wiss. zu Berlin,' 1832. 



^ ' Beitrage zur Kentnniss der Gattungen Campanularia und Syncoryne, Wiegm. Arch.,' 1837. 

 Erster Band, S. 239. 



" It may here be noticed that AV'agner had already (Isis, 1833, § 256, tab. .xi) found medusa-like 

 gonophores, filled with ova iu a hydioid which be names Coryne aculeata, apparently a species of 

 Podocoryne ; but, not being aware of tlie doctrine of Ehrenberg only just announced, tiie exact 

 significance of these bodies escaped him. 



