222 



HARDWICKE'S SCIENCE-GOSSIP. 



generally composed of four joints. Either simple or 

 forked. The posterior portion or tail is generally 

 counted from the segment preceding the sexual organs, 

 which in the female has two small feet (fulcra, Jarine). 

 It is not, however always to be clearly distinguished 

 from the thorax, but it consists of six segments. In 

 the males the second segment is provided with articu- 

 lated processes of variable shapes, relegated to play 

 the part of organs of generation. The female organs 

 are also placed on the second segment. The sixth 

 segment is terminated by two lengthened appendages 

 forming a kind of fork, fringed with extremely fine 

 hairs. 



Specific, Cyclops quadricornis, Muller ; Cyclops vul- 

 garis. Leach ; Monoculus quadricornis, Linn. Abdo- 

 men (apparently the tail) composed of six, sometimes 

 seven segments. Last segment separated at end into 

 two lobes. Superior antenna; composed of a large 

 number of joints (about twenty-eight) ; setae arising 

 from each one. In the male there is a distinct 

 swelling near the middle, followed by a constriction, 

 and a kind of hinge. Antennules largish ; segments 

 four, each one with setae, the last one with six. 

 About one-third length of superior antennae. Man- 

 dibles consist of an oval body terminated with a 

 number of teeth of a brownish colour and a single 

 serrated seta. There is also present a palpus of one 

 segment and two filaments. First pair of foot-jaws 

 each consist of a convex externally and concave 

 internally, body with several strong teeth and a single 

 jointed palpus or rather palp-Uke process, with setae. 

 Second pair of foot-jaws divided into two portions : — 

 an external with four joints and an internal with three. 

 Five pairs of branchial legs arise from the thoracic 

 segments, but the fifth pair are only rudimentary ; in 

 the male they are three jointed, in the female two 

 jointed. Tail two-lobed, each lobe terminated by 

 four setigerous filaments, of which the two inter- 

 mediate ones are the longest. Heart nearly oval, 

 situated under second and third segments of body. 

 It gives off two branches : one to the head, the 

 other to the tail. Below is another organ, also 

 giving off two vessels. Perhaps analogous to the 

 branchiocardiac canals of the decapodous Crustacea. 

 Alimentary canal extending the whole length of 

 body. 



Life-history. — Frequently it will be noticed that on 

 each side of the female is a balloon-shaped sac filled 

 with eggs. These structures are the external ovi- 

 parous pouches or ovaries, and in reality are only 

 continuations of the internal sac, with which they 

 communicate by a minute canal. This fine canal 

 joins the body at the second segment near its junction 

 with the third. At an early stage the eggs are 

 brownish, afterwards gaining a reddish orange colour. 

 The generating power is very great, and one fecunda- 

 tion is sufficient for many generations. Add to this 

 the fact that the female can deposit eggs ten or twelve 

 times per month, and some idea of the amount of 



descendants from a single pair of Cyclops will be 

 obtained. Some writer has computed that one female 

 may be the progenitress of four thousand, five hundred 

 millions, allowing eight ovi-positions of forty eggs to 

 each. The young are extremely unlike the adult 

 animal, as a reference to the illustration will show. 

 At their birth they have only four feet, and their body 

 is without the vestige of a tail.* About twelve days 

 afterwards they acquire another pair of feet (t). After 

 this they undergo their first moult, which transforms 

 them to the adult ; but the feet, antenna, etc., are not 

 even yet perfectly grown. One or two more moults 

 however, and they are at last fully formed and fit for 

 the reproduction of their species. As regards their 

 food, they prefer animal matter but do not scruple, 

 under adverse circumstances, to regale themselves on 

 vegetable. 



Varieties. — Among these are the following : — 

 Rubens : Reddish in colour, sometimes inclining to 

 orange ; eggs brownish, forming oblique masses at 

 the sides of the tail ; length eight-twelfths of a line. 

 Viridis : Green or greenish ; egg masses suspended in 

 a direction a little higher up than the former ; length, 

 nine-twelfths of a line. Fuscus : brownish red ; 

 nearly oval ; egg masses partly covering tail ; length, 

 six-twelfths of a line. Albidus: greyish white, 

 tinged with brown. Egg masses greenish, suspended 

 at nearly a right angle with tail ; length, eight- 

 twelfths of a line. Prasinus : deeper in colour than 

 viridis. Eggs greenish, turning to faint rose colour 

 when about to be hatched ; in two masses seemingly 

 incorporated with the tail ; length, six or seven- 

 twelfths of a line. 



To these I must add descriptions of two more 

 which came under my notice some time ago, 

 viz. : — A variety in which the segments of the 

 abdomen are shorter, appearing as if they had been 

 " telescoped." On a first glance it looks as though 

 the abdomen had been cut off in part. Length about 

 six-twelfths of a line. Colour brownish. I would 

 propose that the name truncatula be applied to this 

 form. The second variety is of the colour of fuscus 

 (Jarine), but more elongated, and the egg masses do 

 not overlap the tail to so great an extent. The 

 antennae are also finer. Length about seven-twelfths 

 of a line. Neither of these two varieties has, to my 

 knowledge, been described before. At the time I 

 came across them I was not so interested in the 

 species, and consequently my descriptions of them 

 were not very minute. I am, however, looking out 

 for more specimens, so as to put on record a better 

 and more complete description. In the meantime 

 some of my readers may perhaps come across them. 

 I shall be glad to receive species for identification at 

 my address as under : 4 Boulton Road, West Bromwich, 

 Staffs. 



* Muller represented them as the genus Amyone at this 

 stage ; and the genus Nauplius at this f. 



