June 1, 1866.] 



SCIENCE-GOSSIP. 



125 



to their species, swell into umbrella-shaped bladders, 

 and become true Acalephaj, resembling some of those 

 beautiful forms so exquisitely depicted by Forbes 

 in] his " Monograph of the Naked-eyed Medusae." 

 Here then we have a creature totally different from 

 its immediate progenitor, the polyp-bearing coral- 

 line. But the wonderful exemplification of the so- 

 called " Alternation of Generations " does not end 



a 



Fig. 116. Free swimming Melicertum. 

 a. Pedicel or proboscis. 



here. The Medusse are furnished with each a pro- 

 boscis or pedicel, really the mouth and stomach of 

 the animal, hanging down from the centre of the 

 umbrella (fig. 4, a) round or upon which, or at- 

 tached to the lobes of the disk, are frequently 

 clustered little gemma?, which are budded off in the 

 way so common with the Actinse, and these become 

 true representatives of their immediate parent ; but, 

 look at these frail, scarcely tangible beauties, which 

 though they have been proved to be perfect radiated 

 animals, and have ever been thought by Steenstrup 

 and Milne Edwards to possess rudimentary organs 

 of sight and hearing, are yet most of them as unsub- 

 stantial as if they were really only the mass of vivified 



Fig-. II". Polgxenia cyanostites, natural size. 



jelly they were so long supposed to be. When left 

 by the tide on the sand, we find only an obscure 

 film of skin, which soon withers away entirely. The 

 utmost delicacy of manipulation, can with difficulty 

 preserve faint traces of them dried on paper. In 

 the celebrated blue grotto of Amalfi (near Naples), 

 myriads of floating fringed balls of sapphire 

 seem to allure the tourist, and tantalize the 

 eye by their brilliant loveliness; but they col- 

 lapse and seem to shrink into impalpability on 

 every attempt to grasp them. Could these 

 creatures, so frail and evanescent, survive the 



buffctings of the rough wintry storms and 

 waves ? Ah, no ! and here we see the efficiency of 

 the remedy provided. Besides the medusoid gemmai 

 budded off, the female perfect medusa produces 

 eggs. These are at first round, then become oval, 

 and clothed with cilia}, so that they can swim freely 

 about ; but becoming oblong pear-shaped, the 

 narrow end at length fixes itself to some safe an- 

 chorage on stone or weed, where the polypidom 

 grows and strengthens, and during this " Nahrungs- 

 Process," as the Germans aptly call it, faithfully 

 nourishes the embryo life, which gradually devclopes 

 the graceful .feathery or moss-like corallines 

 destined to produce the polyp-flowers, which in 

 due course will again become medusas. 



That the exact stages and gradations of these 

 changes of form have not yet been quite clearly 

 observed and described need not be wondered at, 

 when we consider that all these operations are going 

 on in the hidden arcana of that mighty ocean, — 



Where plummet of archangel's intellect 

 Could never yet find soundings, but from age 

 To age let down, drawn up, then thrown again 

 With lengthen'd line and added weight, still faiis ; 

 And still the cry in heaven is, " Oh, the depth ! " 



P. S. B. 



MOUNTING CRYSTALS. 



A FEW remarks, embodying the results of 

 "*-*- personal experience with this class of objects, 

 may not be unacceptable to those readers of 

 Science Gosssir who have but little time to devote 

 to this particular study. Erom books, so far as I 

 am acquainted, but little assistance can be got, as 

 the subject is treated of in so general a manner, that 

 when the student wishes to prepare and mount a 

 special crystal, he is almost always at a loss as to 

 the way in which he should proceed. The method 

 I propose is, to speak of the crystals most usually 

 mounted, and with the preparation of which I am 

 personally acquainted, and if others, whose oppor- 

 tunities and experience are greater than my own, 

 will " follow suit" with descriptions of the mounting 

 of the rarer salts, the list asked for by W. S. in the 

 January number may eventually be completed. 



I must premise that I have no " book-learning" 

 upon the subject ; all the information I possess 

 being the result of many experiments and of nume- 

 rous failures. Still, if by this means I shall have 

 paved the path for others desirous of entering upon 

 the study of this branch of microscopical science, 

 the repayment for the disappointments I have 

 suffered will be ample. 



The crystals referred to above are those of the 

 sulphates of iron, copper, and maguesia, chlorate of 

 potash, tartaric, citric, and gallic acids, salicine, 

 and the mixture of the sulphates of copper and 

 magnesia. 



