HYDROZOA. 



63 



Fig, 13. 



Development of Ttjrbis : — a, ovum of the medusiform zooid {h) 

 known as Turris neglecta ; c, polypite, with creeping hydrorhiza, 

 developed therefrom. (All magnified.) 



Certain medusiform gonophores, and, it may 

 be also, some true Medusids, possess the power of 

 producing, by gemmation, free-swimming forms 

 which directly resemble themselves. Such buds 

 have been observed to start from the sides of the 

 polypite in Sarsia geomnifera and Lizzia octo- 

 ■punctata, from the reproductive region of the 

 calycine canals in two species of Thaumantias, 

 from the bases of the tentacles in Steenstrupia 

 Oiuenii and Sarsia prolifera, and from the de- 

 pendent portion of the tentacles themselves in 

 Diplonema {fig. 14). Hence these medusoids 

 ought, perhaps, to be regarded as free gonoblas- 

 tidia. Here, also, it may be added, that multi- 

 plication by fission has been observed by KolUker 

 in a species of Stomohrachium, 



