154 The Blue Cyancea. 



The ovate organ, so exquisitely fashioned, so liberally fur- 

 nished, and so carefully shielded, presents a beautiful appear- 

 ance when viewed as an opaque object under a strong light, re- 

 flecting a fine yellow colour, and displaying the regularly-shaped 

 extremities of transparent and colourless prisms with which it 

 is filled. As long ago as 1816, Glide* defined these prisms, and 

 some years afterwards Eosenthalf perceived them to be hard 

 corpuscles, and supposed them, since they did not effervesce ivith 

 acids, to be atoms of silicious earth or sand. 



Still later (in 1834) Ehrenberg submitted these marginal 

 organs of the Medusas to an elaborate examination, the results 

 of which he gave as follows : — " The hard bodies are most re- 

 gularly crystallized, water-clear forms, of the crystallization of 

 the quartz-system ; namely, six-sided, short, sometimes nearly 

 globular columns, with a doubly-three-sided or six-sided point. 

 Often they are regularly equal-sided, or longish six-sided tables/ 

 like those formed of carbonate of lime ; not seldom they are 

 long six-sided rods, with unequal flat points ; but always quite 

 distinctly, almost regularly, crystalliforin." The learned pro- 

 fessor then proceeds to tell us how he poured sulphuric acid on 

 the whole sac, with no perceptible result ; how then he crushed 

 down several sacs together, and heated the mass with the same 

 acid, and how the crystals were instantly lost amidst the forma- 

 tion of bubbles. He concludes, therefore, that the prisms are 

 veritable crystals effervescing with acids, and probably consist 

 of carbonate of lime, similar to those which he had previously 

 discovered in vertebrate animals, in connection with the nervous 



cent res .J 



Tims the inorganic earthy crystalline nature of these bodies 

 appeared to be established ; and in the latest work on the ana- 

 fcomy of these creatures — Professor Greene's Manual of the 

 Ccelenterata — the term "lithocyst" is used for the prism-filled 



•, and the prisms themselves are described as " crystalline." 

 STel I am bold to affirm that this is an error. As long ago els 



56 I sta ted, on the ground of my own examinations, a dim rent 

 conclusion. "It docs not appear that these bodies are silicious, 

 or that they are crystals x)f earthy matter at all, hat 

 rattier thai they are composed of hard transparent organic 

 ue, analogous to the crystalline lens in vertebrate animals. 

 Winn treated with liquor potassce they speedily became amor- 

 phous and dissolved into a turbid fluid. Another lot, immersed 

 in citric acid, dissolved in like manner, acquiring a slight tingo 

 of given during I In- process. Not the slightest effervescence or 



burbance v. ible by the most careful -watching under 



either tr< atment."§ 



* Ami. u. V7/y.v. for Medium, pp. is, 28. t Zeittoh. /'. Phjfa., 1826, p. 32G. 

 % MMler* a Archiv, 1884, p. 674. § Tenby, p. 174. 



