130 THE MICROSCOPE AND ITS REVELATIONS. 



tached either to one side only, or to both sides (Fig. 357). In both, the 

 general structure of the individual polypes (Plate xx. , d) closely corre- 

 sponds with that of the Hydra; and the mode in which they obtain 

 their food is essentially the same. Of the products of digestion, how- 

 ever, a portion finds its way down into the tubular stem, for the nour- 

 ishment of the general fabric; and very much the same kind of circula- 

 tory movement can be seen in Campanularia as in Tubularia, the 

 circulation being most vigorous in the neighborhood of growing parts. 

 It is from the ' coanosarc ' (/) contained in the stem and branches, that 

 new polype-buds (b) are evolved; these carry before them (so to speak) a 

 portion of the horny integument, which at first completely invests the 

 bud; but as the latter acquires the organization of a polype, the case 

 thins away at its most prominent part, and an opening is formed through 

 which the young polype protrudes itself, 



520. The origin of the reproductive capsules or 'gonothecae' (e) is 

 exactly similar; but their destination is very different. Within them 

 are evolved, by a budding process, the generative organs of the Zoophyte; 

 and these in the Campanularida may either develop themselves into the 

 form of independent Medusoids, which completely detach themselves 

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

 swim-forth freely, to mature their sexual products (some developing 

 sperm-cells, and others ova), and give origin to a new generation of po- 

 lypes; or, in cases in which the Medusoid structure is less distinctly pro- 

 nounced, may not completely detach themselves, but (like the flower- 

 buds of a Plant) expand one after another at the mouth of the capsule, 

 withering and dropping-off after they have matured their generative pro- 

 ducts. In the Sertularida, on the other hand, the Medusan conforma- 

 tion is wanting, as the gonozooids are always fixed; the reproductive cells 

 (Fig. 357, #), which were shown by Prof. Edward Forbes to be really meta- 

 morphosed branches, developing in their interior certain bodies which 

 were formerly supposed to be ova, but which are now known to be ( me- 

 dusoids' reduced to their most rudimentary condition. Within these 

 are developed, in separate gonothecae, sometimes perhaps on distinct 

 polyparies, spermatozoa and ova; and the latter are fertilized by the 

 entrance of the former whilst still contained within their capsules. The 

 fertilized ova, whether produced in free or in attached medusoids, de- 

 velop themselves in the first instance into ciliated 'gemmules/ which 

 soon evolve themselves into true polypes, from every one of which a new 

 composite polypary may spring. 



521. There are few parts of our coast 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 surfaces 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 

 ( 124). In mounting Compound Hydrozoa, as well as Polyzoa, it will be 

 found of great advantage to place the specimens alive in the cells they 

 are permanently to occupy, and to then add Osmic acid drop by drop to 

 the sea-water; this has the effect of causing the protrusion of the ani- 

 mals, and of rendering their tentacles rigid. The liquid may be with- 

 drawn, and replaced by Goadby's solution, Dean's Gelatine, Glycerine 



