48 



MORPHOLOGY 



comuioTi cavity of the plug-like summit. This has been shown by Agassiz to be the case in 

 his Laomodra {C/i/lia) polerium, and I have myself seen it in a nearly allied species from the cast 



Fig. 19. 



Fig. 18. 



"\\- 



Gonangiiim, with its contents from Laomedea Jlexiiosa. 

 a, Goniingium ; i, blastostyle, carrying gonosacs, wliicli in- 

 crease in maturing from below upwards ; each containing a 

 single ovum in which the germinal vesicle and germinal spot 

 are conspicuous; c, opercular summit of blastostyle; d, common 

 investing meuibrane of the contents of the gonangiutn. 



Gona 



■ith its contents, from Obr-lia geiiiculata. 



a, Cionangium; I, blastostvle loaded with medusa; (blasto- 

 chemes), which increase in maturing from below upwards; 

 c, opercular summit of blastostvle ; d, d, common membrane, 

 investing and confining the medusae 



coast of Scotland (woodcut, fig. 20). It is entirely analogous to the breaking up of the Cffinosare 

 which will be described below as occurring in the stem of Antennularia. 



In most cases the gonophore discharges its generative elements directly into the surrounding 

 water. In the females of some calyptoblastic species, however, the ova, instead of escaping directlv 

 from the gonoi)hore into the water or the cavity of the gonaiigium, are retained for some time in a 

 peculiar receptacle, where they undergo further development, and which is supported upon the 

 summit of the gonangium, and lies entirely external to its cavity (woodcuts, figs. 3, n, 21 and 22). 

 It will be found convenient to employ a special term for this receptacle, which confers upon the 

 gonosomes in which it occurs a very characteristic feature. I have already designated it by the 

 name oS. " acroci/d}" It may be seen in Serftdaria pumila, S. cupressina, S. polyzonias, Calycella 

 gi/riiif/a, Calycella laceraia, &c., and would seem to be in every instance confined to the female. 



^ 'Pioc. Roy. Soc. Edin./ 1858. 



