June 15, 1883.] 



• KNOWLEDGE 



>59 



stick. This will catch the free swimmers. A hook at the 

 end of a stick will facilitate pullinj:; out pond weeds, and a 

 small curved knife, instead of the 1 ilunt hook, is handy for 

 cutting; oft' portions of niyriophyllum, anacharis, or other 



2. Brachionns nrceolaris, remarkable, amongst other things, for 

 its highly-organised tail, which it flaps like a cat. 



plants on which the tube dwellers may have erected their 

 houses. Mr. Baker, in High Holborn, Mr. Stanley, and 

 many other opticians, sell walking-sticks containing a fish- 

 ing-rod joint to extend their length, and with a handy 



3. CEcistes crvstallinns. 



way of attaching the bottle, hook, or knife. Besides the 

 capturing-lx)ttle, a larger one should be taken to hold the 

 spoil, which a hand-magnifier is usually suiEcient to indi- 

 cate. 



In other papers, opportunity will be found for describing 

 in detail some of these interesting creatures. At present 

 we niaj- consider some of the leading peculiarities of the 

 family. Comparative anatomists put them amonijst the 

 6'ctilecHlfi; a group that includes the intestinal worms. 

 The arrangement is not very satisfactory, as most of the 

 rotifers are superior in organisation to any of these worms 

 in any of their stages ; they all, however, agree in pos- 

 sessing a peculiar set of vessels called " a water vascular 

 system," communicating with the exterior, and probably 

 subservient to excretory processes. Female rotifers 

 are furnished with a gullet, a masticating apparatus, 

 commonly called a gizzard, but which in several species 

 can be protruded as a prehensile mouth. They also have 

 a stoniacli, and an intestine ending in a cloacal opening, 

 except in one genus. All have a nervous system. The 

 larger carapaced sorts show a conspicuous cerebral gan- 

 glion, which is not difficult to see in most others, but the 

 ramifications of the nerves are more or less untraceable. 

 They have no blood circulation. Their ciliary apparatus 

 is very complex. Most commonly they bring all the light 

 floating matter around them near their mouth-opening by 

 means of the whirlpools which they excite ; but as the 

 observer watches them he will see that they can produce 

 other currents to cause the particles they want to pass 

 down into the gullet, and onwards through the gizzard, 

 while other particles they find unsuitable are hurled away. 



Most of them have little red eyes, which glisten like rubies 

 when well lit up. These organs seem to have a cornea and 

 a lens, and sometimes disappear in the adult stage. The 

 alimentary canal is lined with cilia, and in one genus, 

 aspJanchna (which have no anal aperture), the digestive 

 process is assisted by very strong currents produced by 

 cilia that are conspicuous under high powers. 



Male rotifers are scarce, and those of many species have 

 not been disco\ered. They are only wanted at certain 

 times, and then not for long, so they are not provided with 

 any alimentary apparatus. The females produce a plen- 

 tiful supply of eggs, which are mostly hatched externally ; 

 but in the common rotifer, and some others, the young ones 

 may be seen inside their mothers, and working their tiny 

 gizzards or jaws. Opportunities will occur for describing 

 the structure and ways of individuals of this interesting 

 family, and, meanwhile, the figures now given will help the 

 Ijeginner to recognise some of the most striking forms. 



These figures are taken from " Marvels of Pond Life," 

 by permission of Messrs. Groombridge it Sons They are 

 drawn as they are easily seen, and many interesting parti- 

 culars will be found in the work they belong to. 



Time Signalling. — In the annual report of Mr. "W. H. 

 M. Christie, astromer royal, he says : — " There has been no 

 case of failure in the automatic drop of the Greenwich 

 timeball. On three days the ball was not raised on account 

 of the violence of the wind. The Deal ball has been 

 dropped automatically at 1 p.m. on every day throughout 

 the year, with the exception of five days on which there 

 was a failure in the telegraphic connection, of one day 

 when the ball was accidentally dropped 4 sec. too soon by 

 telegraph signals, and of fourteen days when the current 

 was weak and the trigger was released by the attendant. 

 On twelve days the ball was not raised because of the 

 violence of the wind. The Westminster clock has main- 

 tained its high character, its errors having been under 

 1 see. on OG per cent, of the daj's of observation, between 

 1 sec. and 2 sec. on 25 per cent., between 2 sec. and 3 sec. 

 on 6 per cent., and between 3 sec. and 4 sec. on 3 per cent. 

 The error has never exceeded 4 sec." 



