RELATIONSHIP OF MEDUSA TO HYDROZOA. 467 



peculiarly fitted for Mr. Furze's combination of the polarizing 

 plate with the spotted lens (§ 63) ; as they then exhibit all the 

 richness of coloration which the former developes, with the pe- 

 culiar solidity or appearance of projection which they derive from 

 the use of the latter. 



306. 'No result of Microscopic research has been more unex- 

 pected, than the discovery of the close relationship subsisting 

 between the Hydroid Zoophytes and the Medusoid Acalephse (or 

 jelly-fish). We have seen that many of the small free-swimming 

 Medusans, belonging to that simple tribe of which Thaumantiaa 

 (Fig. 225) may be taken as a representative, are really to be 

 considered as the detached sexual apparatus of the Zoophytes 

 from which they have been budded oft", endowed with indepen- 

 dent organs of nutrition and locomotion, whereby they become 

 capable of maintaining their own ex- 

 istence and of developing their gene- Fio. 225. 

 rative products. The general confor- 

 mation of these organs will be under- 

 stood from the accompanying figure. 

 Many of this group are very beautiful 

 objects for Microscopic examination, 

 being small enough to be viewed entire 

 in the zoophyte-trough. There are few 

 parts of the coast on_ which they may Ti.auma.nuasjZeiu, one of .he 



not be found, especially on a calm " naked-eyed" Medus£e:-a a, oral 



warm day, by skimming the surface of tentacuia; b, stomach; c, gasiro- 

 the sea With a fine muslin net attached "."^""J*; >=-"^l^. >'='ving the ova- 



, i-T •.! -i o t Tie.Sj da, on either side, and ter- 



to a ring, which may either be fixed to minaling in the marginal canal.ee. 



the end of a stick held in the hand, or 



may be fastened by a string to the stern of the boat as a tow-net. 

 In either case, the net should be taken up from time to time, 

 held so as to allow the water it contains to drain through it, and 

 then turned inside out (so that what was previously its internal 

 surface shall now be the external), and moved about in a bucket 

 of water, so that any minute animals adhering to it may be 

 washed oS. When we turn from these small and simple forms, 

 to the large and highly-developed Medusans which are com- 

 monly known as "jelly-fish," we find that their history is essen- 

 tially similar; for their progeny have been ascertained to 

 develope themselves in the first instance under the polype form, 

 and to lead a life which in all essential respects is zoophytic ; 

 their development into Medusas taking place only in the closing 

 phase of their existence, and then rather by gemmation from 

 the original polype, than by a metamorphosis of its own fabric. 

 The embryo emerges from the cavity of its parent, within which 

 the first stages of its development have taken place, in the con- 

 dition of a ciliated gemmule, of rather oblong form, veiy 

 closely resembling an Infusory animalcule, but destitute of a 

 mouth. One end soon contracts and attaches itself, however, so 



