COLLECTION AND OBSERVATION OF HYDKOZOA. 465 



Zoophyte; and these sometimes develope themselves into the 

 form of independent Medusae, which completely detach them- 

 selves from the stock that bore them, make their way out of the 

 capsule, and swim forth freely, to mature their sexual products 

 (some developing spermatozoa, and others ova) and give origin 

 to a new generation of polypes ; whilst in other cases, these 

 flower-buds, whose Medusan structure is less distinctly pro- 

 nounced, do not completely detach themselves, but expand 

 one after another at the mouth of the capsule, withering and 

 dropping off after they have matured their generative pro- 

 ducts ; and in other cases, again, the Medusan conformation is 

 altogether obscured by want of development, the sexual act 

 being performed by those bodies whilst they are still enclosed 

 within their capsules. There is reason to believe that the male 

 and female Medusoids are always developed within separate cap- 

 sules, possibly on distinct polypidoms ; the males give forth 

 spermatozoa ; whilst the females prepare ova, which, when ferti- 

 lized by the entrance of spermatozoa, develope themselves into 

 ciliated " gemmules," and these, escaping from the capsules, 

 soon evolve themselves into true polypes. This last is the only 

 mode of generation that has been yet witnessed among the Ser- 

 tularidce ; for no free Medusoids have been observed to make 

 their way out of the capsules of any members of this family 

 (Fig. 224), within which may be seen several bodies that are 

 commonly reputed to be eggs, but are really imperfectly de- 

 veloped gemmae of the Medusan type. It is worthy of notice, 

 that the horny capsule has been shown by Prof. E. Forbes, to be 

 essentially a metamorphosed branch, whose numerous small 

 cells have coalesced (as it were) into a single large one ; this is 

 made obvious by a careful comparison of the forms under which 

 it presents itself, in different members of these two families. 



305. There are few parts of our coasts, which will not supply 

 some or other of the beautiful and interesting forms of Zoophytic 

 life which have been thus briefly noticed, without any more 

 trouble in searching for them, than that of examining the sur- 

 faces of rocks, stones, sea-weeds, and dead shells between the 

 tide-marks. Many of them habitually live in that situation ; and 

 others are frequently cast up by the waves from the deeper 

 waters, especially after a storm. Many kinds, however, can only 

 be obtained by means of the dredge. For observing them during 

 their living state, no means is so convenient as. the zoophyte- 

 trough (§ 69), invented for that express purpose by Mr. Lister, 

 to whom we owe not only many improvements in the Microscope 

 and its appurtenances, but also some of the earliest and best ob- 

 servations upon this class of Zoophytes which the application of 

 the Achromatic principle permitted. Before mounting them for 

 preservation as microscopic objects, the Author has found it best 

 to keep them for some time in strong spirit; after a prolonged 

 maceration in which, they may be mounted in spirit sufliciently 



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