July 1,1865.] 



SCIENCE-GOSSIP. 



159 



give off a series of delicate branching filaments 

 termed setm. These are as transparent as spun 

 glass, and add greatly to the beauty of the anteunse. 

 The inferior or smaller pair, which have their origin 

 behind the first, are considerably shorter, have fewer 

 divisions, and are much less elegant. In the males 

 the form of the autennaj is somewhat different, and 

 serves to distinguish the one sex from the other. 

 They are less elegant in their outline, are also 

 shorter and thicker, and swell somewhat towards 

 the tips, which end in a hinge-joint peculiar to the 

 male (fig. 1). The mandibles, foot-jaws (the latter 

 being so named from partaking of the character of 

 both feet and jaws), the mouth, and first pair of feet 

 are all included within the protecting compass of the 

 first shield-shaped segment. The remaining divisions 

 include the swimming-feet, viscera, and reproductive 

 organs. 



Fig- 1. Pig. 2. Fig-. 3. 



The general form of the Cyclops quadricornis is 

 ovoid or club-shaped, being broad and rounded at the 

 head, with a gradual tapering off towards the tail, 

 which ends in two long lobes, embellished with 

 delicate transparent setee of unequal length; thus 

 forming an elegant plumose termination to this end 

 of the body. 



In its progress through the water the Cyclops 

 moves with a rapid jerking motion, which may be 

 very weU observed by placing the animal between 

 the eye and the light. It will then be seen that its 

 principal propeUiug organs are its oar-like feet, of 

 which it has five pairs. Each foot, which may be 

 said to be double^ consists of a common stem, from 

 whence arise two jointed branches, which are 

 liberally supplied with setse, or bristle-like appen- 

 dages. The fifth pair are, however, rudimentary, 

 and in the two sexes differ in form. 



Erom the abundance of this little animal in every 

 stagnant pool and ditch, we may naturally infer that 

 its mode of increase must be exceedingly rapid. The 

 pond from whence we obtained our supply seemed 

 to be hterally alive with Cyclops and Water-fieas. 

 In the former the females greatly preponderated, 

 and could be easily distinguished from (;he males by 

 their external ovaries, which hung suspended on 

 each side of their bodies like miniature clusters of 



grapes. The number of eggs contained in each 

 ovary varies from thirty to forty. Jurme, who made 

 a careful calculation to show the wonderful fecim- 

 dity of this species, reckons that one female in the 

 course of twelve months would become the pro- 

 genitor of 4,443,189,120 young. As it does not 

 appear that the eggs increase in size while in the 

 external ovaries, although they undergo a change of 

 colour, and as experiments have shown that they 

 retain their vitality even when the parent has been 

 killed, most naturalists are disposed to consider this 

 crustacean as oviparous. Nothing can be more un- 

 like its parent than the young Cyclops when it first 

 escapes from the ovary (fig. 2). Indeed, so great is the 

 dissimilarity, that the older naturalists were deceived, 

 and formed these imperfect individuals into a dis- 

 tinct genus, although Leeuwenhoek had previously 

 pointed out their true relationship. In tlie early 

 days of our microscopic inquiry — why should we be 

 ashamed to confess it — we fell into a similar error; 

 and no one, v/e believe, unless he had carefully 

 watched the Cyclops from its bii'th to maturit}^, 

 would ever have suspected the parentage. Erom 

 the observations of Baird and others, it appears that 

 a period of seventeen to twenty days is required to 

 perfect the form of the young Cyclops. During this 

 period it moults three times ; at every moult it 

 assumes a form more approximate to its parent. In 

 getting rid of its cast-off clothes, it sometimes falls 

 a victim to the process. These exuvise, however, 

 are most beautiful objects when seen by the micro- 

 scope, presenting, as they do, a perfect cast of tlie 

 creature's form, with all its articulations and deli- 

 cate plumose setse entire. It is always desirable to 

 mount these casts permanently, as they form in- 

 structive objects, showing the gradual approach of 

 the Cyclops towards its perfect state or form. Per- 

 haps the best method of permanently preserving 

 such objects is to soak the object itself for a few 

 days in glycerine ; then place it with some of the 

 fluid in a cell formed of Brunswick-black, and her- 

 metically seal a thin glass cover over it with gold 

 size. If the angles between the cover and the cell 

 are gradually filled up with the Brunswick -black, 

 the preparation will keep for years. The Cyclops, 

 though exceedingly rapid in its increase, is 

 thoroughly kept in check by the numerous enemies 

 which surround it on all sides. Millions fall vic- 

 tims to trout and other kinds of fish ; and the deli- 

 cious, delicate flavour of the former is said to be in 

 a great measure owing to a plentiful supply of this 

 living food. The Hydree, and the larvse of aquatic 

 and land insects, all play their part in the work of 

 destruction, and thus lend a helping hand in keeping 

 down that teeming abundance of life whicn would 

 otherwise choke up our ponds, ditches, and streams, 

 with animal life, until existence under such circum- 

 stances would become an impossibility. — T. K. 



