34 FRESHWATER LIFE. 



bristles. The first segment of the abdomen is small, and carries a fifth 

 pair of feet, modified in both sexes to subserve the reproductive process. 

 In the male the next two segments are distinct ; in the female not. The 

 larger antennae of the male swell out about the middle, and make a hinge- 

 joint behind the swelling, peciiliarities wanting in those of the female. 

 The adult female, in the breeding season, carries two external ovisacs, 

 fastened one on each side, near the base of the abdomen. They must 

 not be confounded with the true ovaries, which are internal. They are 

 only a temporarj^ shield, secreted by the female around each bundle of 

 eggs at the time of laying them, and are ruptured and finally shaken off 

 when the eggs are hatched. Lastly, one eye placed in the front of the 

 head serves as the single organ of vision. It is often of a brilliant ruby 

 colour, especially in j'oung specimens. 



As in most other genera so in this, the females are much more 

 numerous than the males. The fact is no doubt connected with another 

 pecuharit\', which has been termed paiiihenogenesis. One impregnation 

 enables a female Cyclops to go on laying successive batches of eggs for 

 life. And the female progeny are themselves fertile, though carefully 

 isolated as soon as born ; and so on for several generations. The rate of 

 increase of some species of Entomostraca is enormous. According to 

 Jurine it is quite possible for a single female to be the progenitor during 

 one year of many millions of young. But, practically, the rate of increase 

 is checked by various aquatic enemies, the vast majority of the young 

 being simply born to be eaten. There are few more intei'cstiug spectacles 

 under the microscope than the hatching of a brood of Cyclops. When the 

 time draws near the little things are seen all huddled together in a 

 cluster, each in its separate pocket of the ovisac, peeping through the 

 membi'anous veil with bright ruby-coloured eye. You single out one for 

 special observation, and feel a growing interest as you watch the repeated 

 struggles of the tiny prisoner, its final escape, and its first joys of liberty, 

 as it darts away in the surrounding water, with the jerky, zigzag motion 

 of its parent. Nor is it less interesting afterwards to note from day to 

 day the changes of form and successive moultings by which the adult 

 state is reached. Tlu'ee moultings take place before the animal is perfect, 

 and capable of producing its species. 



Nearly related to Cyclops, and not much unlike it in appearance, is 

 Cantlioraiiiptiis, found abundantly in the ponds about Ts'ottiughani. As it 

 is rather small, the best way to secure a specimen for examination is to 

 place a portion of the gathering in a shallow dish, and look it well over 

 with a pocket lens. A small dipping tube, made as follows, will be found 

 useful : — One end must be drawn to a blunt point with moderate aperture, 

 the other inserted into a short piece of india-rubber tubing, sealed air 

 tight at the free extremity. The length of the glass part may be about 

 two inches. Press the india-rubber between thumb and fore-finger, dip 

 into the water, and by removing pressure at the right moment the 

 object is sucked up into the tube, whence it may be expelled by once 

 more pinching the india-rubber. The two commonest species of Cantho- 

 camptus are C. miiiiitu.'; and C. furcatus. In the female I have often 

 found a curious reddish structure coming off fi-om the sixth body segment. 

 It is of a hard and horny nature, but its use is not known. Closely 

 allied to the preceding is Diajytomm caiitof, easily recognised by its inferior 

 antennae, which are fully as long as the entire body. I have found it 

 amongst algae in stagnant drains. 



Animals belonging to the first two ordei-s of Entomostraca have 

 coruparatively few brauchiaj, and these attached to the appendages of 

 the mouth. Animals belonging to the remaining two orders have many 

 branchiaj, and these attached to the legs, which are often numerous. 



