HA R D Wl CKE 'S S CIENCE -GOSS IP. 



137 



floor would have the mouth downwards. Both mouth 

 and anus are usually present on the upper surface of 

 the body of a Crinoid, the anus often terminating a 

 nipple-shaped protuberance. In the most ancient 

 Crinoids there seems to have been a difference from the 

 structure seen in their living representatives. If we 

 carefully examine the arms of recent Crinoids we see 

 that they are ftirrcnoed on the upper surface. Both 

 the arms and the pimiDs which give to them such a 

 feathered appearance are formed of an immense 

 number of limy joints. (In the extinct Pentacrinus 

 briarcus, found so abundantly in the Lias near 

 Whitby, it is estimated that no fewer than one hun- 

 dred and fifty thousand joints are employed in the 

 construction of the five pinnated arms of one indivi- 

 dual !) All are alike grooved on their upper surface, 

 and thus we have channels or gutters running over 

 every part of the upper surface of each arm. All is 

 covered by a membrane or skin, which not only keeps 

 the ossicles together, but is itself covered with 

 thousands of minute cilia. The latter are movable, 

 and are, as most of our readers are aware, a kind of 

 motive machinery much in use among all kinds of the 

 lower forms of aquatic life. The consequence of the 

 general action of these vibratile cilia over the entire 

 upper surface of the arms of the Encrinites is that 

 currents of water bearing food are constantly being 

 deflected down the bases of the five arms. The main 

 grooves of these are continued over the surface of the 

 body of the Encrinite, and all converge toward the 

 mouth, which is thus supplied with fresh food and 

 fresh water. 



In the Palaeozoic Crinoids the arms are grooved 

 above, but the grooves terminate at their bases, and 

 do not continue over the surface of the body, as above 

 described. Instead of this they open into tunnels 

 or channels, which are excavated, so to speak, in 

 the under-surface of the limy plates, and thus reach 

 the mouth of the Encrinite beneath the plates, instead 

 of from above. The arms of Encrinites are not 

 hollow, as is sometimes supposed, but formed of solid 

 joints or ossicles, as they are scientifically called. The 

 joints of the stem, on the contrary, have a cavity 

 running down their middle, of various shapes, some- 

 times round, and frequently petal-shaped into five 

 radiating arms. This continued hollow was formerly 

 believed to be a continuation of the alimentary canal, 

 but the notion is incorrect. The joints of the stems of 

 all species of Encrinites are either grooved or toothed 

 along their margins. In this way they were firmly 

 interlocked, and yet were so capable of free move- 

 ment that there is no doubt the whole Encrinital 

 structure was swayed about by the tides and currents as 

 freely as any of our larger rooted sea- weeds. From 

 what we have said as to the pinnated arms of 

 Crinoids, it will be seen that the old notion of their 

 being so many nets in which to catch organic waifs 

 and strays, is a good way from the truth. In com- 

 parison with the size pi the entire structure, the 



stomach is wonderfully small, and enclosed in the 

 large and densely-plated body. Some of the carboni- 

 ferous Encrinites must have had stems of enormous 

 length, judging from the strength and diameter of the 

 joints. In the Yoredale shales of the valleys running 

 from Hebden Bridge to Halifax, in Yorkshire, we have 

 disinterred and exposed connected stems of Encrinites 

 ten feet in length, the ossicles of which were not a fourth 

 part the diameter of those to be abundantly met with 

 in the Carboniferous limestones of Derbyshire. 



In our next article we propose describing the chief 



generic types, and the localities where they most 



abound in the fossil state. 



( To be continued. ) 



MICROSCOPY. 



MiCROSPECTROSCOPES. — The proposition I should 

 like to make through the medium of your journal is 

 one which I at least, though apparently alone, would 

 most willingly be always glad to do something for. I 

 would speak to those who have a microspectroscope. 

 Is it not in many cases purchased to be pul into one's 

 case that people shall say ' ' What a perfect set of 

 instruments !" or ai-e its revelations too abstruse ? 

 Surely this cannot be, for those things which have the 

 character of being abstruse seem to be most sought 

 after. The fact is, that its use is not even realized as 

 an addition to our microscopes. I have been a 

 student at it now for over three years, and my 

 experience tells me that we owe to Mr. H. C. Sorby 

 a great deal, and should show forth those feelings of 

 gratitude by forming in some way a community of 

 combined workers who could compare measurements 

 and so perhaps bring forth some good fruit. I would 

 therefore propose that some of your readers who have 

 worked at this instrument should develope (through 

 your journal) this research more generally. An 

 exchange, or rather a post-box, to contain tubes, might 

 be kept in circulation, and worked on the same rules 

 as one we all know of, which sends slides for the 

 microscope. As to the supposed difficulty of 

 measurement, that is overcome: the correct one is, of 

 course, wave-lengths, and any measurements expressed 

 should be always quoted by that standard, by which 

 alone it appears possible to establish formuke. — TJios. 

 Palmer. 



Microscopical Societies. — TheQuekett Micro- 

 scopical Society held their annual soiree in University 

 College on April 13th. The tables were as usual 

 crowded with microscopes, and most of the new 

 microscopical and mechanical appliances to these in- 

 struments were to be seen in working order. The 

 list of objects exhibited was both large and various. 

 The soiree was a complete success in every way, and 

 it is gratifying to find the efforts of the committee and 

 secretary so highly appreciated. The Medical Micro- 



