BRANCHIOPODS — TENACITY OF LIFE. 545 



tennse), whence it has received the name of Oheirocephalus ; but 

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

 animal being vegetable, and their function is to clasp the female 

 in the act of copulation. The Branchipus or Oheirocephalus is 

 certainly the most beautiful and elegant of all the Entomostraca, 

 being rendered extremely attractive to the view by the "unin- 

 terrupted undulatory wavy motion of its graceful branchial feet, 

 slightly tinged as they are with a light reddish hue, the brilliant 

 mixture of transparent bluish green and bright red of its pre- 

 hensile antennse, and its bright red tail with the beautiful plu- 

 mose setse springing from it:" unfortunately, however, it is a 

 comparatively rare animal in this country. The Artemia salina 

 or " brine shrimp" is an animal of very similar organization, 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 abun- 

 dant, as to communicate a red tinge to the liquid. 



369. Some of the most interesting points in the history of the 

 Entomostraca lie in the peculiar modes in which their Generative 

 function is performed, and in their tenacity of life when desic- 

 cated, in which last respect they correspond with many Rotifera 

 (§ 280). This provision is obviously intended to prevent them 

 from 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." It 

 does not appear, however, that the adult animals can bear a 

 complete 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 con- 

 tinued 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 temperature, and thus continue the 

 species which would otherwise be exterminated. Again, we 

 frequently meet in this group with that reproduction by gemma- 

 tion, which we have seen to prevail so extensively among the 

 lower Eadiata and Mollusca. 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 ; whilst the latter continues at all periods of the year, so 

 long as warmth and food are supplied, and is repeated many 

 times (as in the Hydra), so as to give origin to as many succes- 

 sive ^'broods." Further, a single act of impregnation serves to 



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