Sept. 1, 1S70.1 



HARDWICKE'S SCI EN CE-GOSSIP. 



197 



work, "The British naked-eyed Medusae," from 

 which we borrow a drawing and a few particulars 

 for the benefit of those who cannot possibly refer to 

 the work itself. 



"At the base of the marginal tentacula there are 

 present in a great many of these animals coloured 

 spots or bulbs; in some species these points are 

 very strongly coloured, and from their magnitude 

 indicate the course of the animal when in motion, 

 appearing like a circle of gems in the water. When 

 these bulbs are examined under the microscope, we 

 find their organization more complicated than at 

 first glance it would seem to be. In the majority of 

 species, perhaps in all, these bulbs, whether con- 

 spicuous from colouring or not, contain a small 

 cavity quite distinct from any coloured spot which 

 may be present. The former is the otolitic vesicle, 

 the latter the ocellus." The otolitic vesicle, which, 

 from analogy and its peculiar structure, is con- 

 sidered an organ of hearing, is a small spherical sac 

 developed in the midst of the granular substance of 

 the bulb, and containing more or fewer vibrating 

 bodies : these vibrating crystals or otolites have been 

 distinctly seen in motion, and chemical tests have 

 shown them to be calcareous. The ocelli, from 

 analogy, are regarded as rudimentary eyes, or rather, 

 light-perceiving organs : they vary greatly both in 

 colour and complexity of construction. " That these 

 bodies are the eye-spots, there can be no doubt, when 

 we compare them with similar bodies in the higher 

 Medusae." In them crystals are present, which 

 have been shown by Rosenthal to be silicious, a 

 character by which they are strikingly distinguished 

 from otolitic crystals, which are always calcareous. 



Fig. ISO. Marginal bulb, with ocelli and otolites of Oceania 

 turrita x 25, after Forbes. 



In fig. ISO, d marks the upper end of the ten- 

 tacle immediately below the bulb, which contains (Jb) 

 the otolitic vesicle with its iucluded crystals; c, 

 the crimson ocellus ; i, marginal bulbs bearing the 

 rudimentary ocelli (a). 



Of all the exquisitely beautiful things that fre- 

 quent our seas none can surpass our fair Cydippe, 

 one of the Ciliograde acalephee. If we had time, we 

 should go into raptures about the crystal globe, the 

 eight costal bands of cilia, the long retractile ten- 

 tacles, and a dozen other things ; we can only re- 

 mark that the learned have had a grand dispute 



about the situation of her mouth. Reasoning from 

 analogy, one might expect that the mouth would be 

 situated between the tentacles at the lower pole of 

 the globe ; but Nature has thought proper to place 

 the "buccal orifice" at the upper, and not at the 

 lower extremity. The oldest drawing published 

 shows the mouth at the wrong end, and, as is the 

 case with natural history illustrations in general, 

 this poor old plate has been sedulously copied, blun- 

 ders and all, into almost every book in which Oydippe 

 has been mentioned, for the last forty years. 



Fig. 181. Cydippe pileus. 



Although we had seen Cydippe swallow coloured 

 objects by the upper orifice, and eject refuse matter 

 by the lower one, we might still have yielded to the 

 dictum of "the authorities," had we not come across 

 the positive declaration of Owen, that the mouth of 

 our heroine is at the upper pole of the globe, while 

 the cloacal canal terminates in two small excretory 

 ducts at the other extremity. 



This shrimp-like fellow, half an inch in length, of 

 a brilliant crimson hue, mottled with spots and 

 patches of white, is Amphithoe mbricata, a natatory 

 amphipod of the nest-building order. 



We are chiefly indebted to Mr. Spence Bate for 

 our knowledge of the habits of the curious crusta- 

 ceans who construct abodes in which they take 

 shelter and bring up their families. Writing of our 

 Amphithoe, he says : "This animal generally lives in 

 a nest of its own construction. Its common resting- 

 place is at the roots of Lamina/rice and other plants, 

 or on the under sides of stones, at the bottom of the 

 sea in a few fathoms of water, seeking some secure 

 nook or quiet corner in which to dwell in peace and 

 safety. Some specimens which we kept alive, built 

 for themselves nests against the surface of the glass 

 vessel in which they were confined. On the side of 

 the vessel grew young fronds of weed ; each posi- 

 tion which was selected by one of the animals for 

 its abode was swept clean for a distance round the 

 nest by the long antennae, proving distinctly that 

 the animal reaches out and collects material to 

 assist in the construction of its cell. Upon placing 

 one of these newly- constructed dwelling-places 

 under the microscope, we found that the many bits 

 of weed, chiefly green ulva, were matted together 

 by some exquisitely delicate fibres. This fibrous 

 material possessed the appearance of having been 

 spun or twisted, since frequently small loops were 

 formed by a fibre having been twisted upon itself. 



