ENTOMOSTRACA 963 



these are not used by it for the seizure of prey, as the food of this 

 animal is vegetable, but to clasp the female in the act of copulation. 

 The Sranchipus or Cheirocephalus is certainly the most beautiful and 

 elegant of all the Entomostraca, being rendered extremely attractive 

 to the view by ' the uninterrupted undulatory wavy motion of its 

 graceful branchial feet, slightly tinged as they are with a light red- 

 dish hue, the brilliant mixture of transparent bluish-green and bright 

 red of its prehensile antennae, and its bright red tail with the beauti- 

 ful plumose setre springing from it.' Unfortunately, however, it is 

 a very rare animal in this country. The Artemia salina, or ' brine- 

 shrimp,' is an animal of very similar organisation, and almost 

 equally beautiful in its appearance and movements, but of smaller 

 size, its body being about half an inch in length. Its ' habitat ' is 

 very peculiar, for it is only found in the salt-pans or brine-pits in 

 which sea- water is undergoing concentration (as at Lymington) ; and 

 in these situations it is sometimes so abundant as to communicate a 

 red tinge to the liquid. 



Some of the most interesting points in the history of the Ento- 

 mostraca lie in the peculiar mode in which their generative function 

 is performed, and in their tenacity of life when desiccated, in which 

 last respect they correspond with many Rotifers. By this pro- 

 vision they escape being completely exterminated, as they might 

 otherwise soon be, by the drying up of the pools, ditches, and other 

 small collections of water which constitute their usual habitats. 

 We do not, of course, imply that the adult animals can bear a com- 

 plete desiccation, although they will preserve their vitality in mud 

 that holds the smallest quantity of moisture ; but their eggs are 

 more tenacious of life, and there is ample evidence that these will 

 become fertile on being moistened, after having remained for a long 

 time in the condition of fine dust. Most Entomostraca, too, are 

 killed by severe cold, and thus the whole race of adults perishes 

 every winter ; but their eggs seem unaffected by the lowest tempera- 

 ture, and thus continue the species, which would be otherwise ex- 

 terminated. Again, we frequently meet in this group with that 

 agamic reproduction which we have seen to prevail so extensively 

 among the lower forms. In many species there is a double 

 mode of multiplication, the sexual and the non-sexual. The 

 former takes place at certain seasons only, the males (which are 

 often so different in conformation from the females that they would 

 not be supposed to belong to the same species if they were not seen 

 in actual congress) disappearing entirely at other times. The latter, 

 on the other hand, continues at all periods of the year, so long as 

 warmth and food are supplied, and is repeated many times so as to 

 give origin to as many successive ' broods.' Further, a single act of 

 impregnation may serve to fertilise, not merely the ova w r hich are 

 then mature or nearly so, but all those subsequently produced by 

 the same female, wrhich are deposited at considerable intervals. In 

 these two modes the multiplication of these little creatures is carried 

 on with great rapidity, the young animal speedily coming to maturity 

 and beginning to propagate, so that, according to the computation 

 of Jurine, founded upon data ascertained by actual observation, a 



3 Q 2 



