216 



NATURAL HISTORY. 



the shell. This is what Miiller calls the ephippium, from the resemblance it bears to a saddle. But 

 though he describes it well, he does not give any opinion upon the cause or use of the formation. 

 Straus, however, has proved it to be an inner bivalved case or shell, containing two eggs, destined, 

 he says, for perpetuating the species in the spring : these eggs resisting the cold of winter, which 

 proves fatal to the perfect animal." 



FIFTH LEGION. LOPHYROPODA. 



The LOPHYROPODA, or stiff Hair-footed Crustacea, form the second division of the Entomostraca. 

 The same simple structure is repeated as in the BRANCHIOPODA, with but slight variations in the 

 organs of locomotion. 



ORDER X. OSTRACODA. 



In the fresh-water Cypris and the salt-water Cythere the body is enclosed in a bivalved shell. 

 Dr. Baird says of Cypris : " When the ponds and ditches in which they live dry up in summer, 

 they bury themselves in the mud, and thus preserve their lives as long as the mud retains any 

 moisture, becoming as active as ever when, the rain falls and again overflows their habitation. After 

 long-continued drought, however, when the mud becomes very dry and hard, they perish ; but 

 the eggs do not perish with the parents, for they can be hatched in four days after being placed in 

 water. These little creatures seem to be very lively in their native element, being almost constantly 

 in motion, either swimming about rapidly by the action of their antennae, or walking upon the 

 plants and other solid bodies floating in the water." 



The Cythere are minute marine Crustacea, and are met with in pools amongst the rocks along 

 the coast. "These animals," says Dr. Baird, "have never been seen to swim, invariably walking 

 among the branches and leaves of the Confervse or Fuci, &c., where they delight to dwell. When 

 shaken out from their hiding-places into a bottle or tumbler of water, they may be seen to fall 



in gyrations to the bottom, without ever attempt- 

 ing to dart through the watery element, as is 

 the case with the Cyprides. Upon reaching 

 the bottom, they open their shells and creep 

 along the surface of the glass, but when touched 

 they immediately again withdraw themselves 

 into their shell, and remain motionless. Their 

 inability to swim is, no doubt, owing to the want 

 of the pencils of long hairs or filaments which 

 adorn the superior and inferior antennae of the 

 Cyprides." 



ORDER XI. COPEPODA. 



Fig. 39. FORMS OF CLADOCERA, OSTRACODA, AND COPEPODA. 



&S3&SS 



^ u tne fresh-water Cyclops and the marine Ceto- 

 (Fig. 39) the head and thorax are covered by 

 a shield, and the posterior abdominal segments are 

 distinctly seen. The long antennae in the latter 



forms serve as oars to propel the animal through the water. How great must be the numerical 

 strength of the species in these lower forms, when Cetochilus so minute can yet colour the sea for 

 miles in extent, and furnish abundant food for so large a mammal as the Whale ! 



The various species of the genus Cyclops abound in inland waters all over the world, being 

 essentially fresh-water animals, in a few cases only inhabiting slightly brackish water. They are 

 amongst the most abundant of all the individuals of the order. The young stages of Cyclops have 

 been named as distinct species, the same animal having been honoured with four or five different 

 titles between birth and maturity. The full-grown female is often of considerable size. The eggs 

 are carried in pouches, and are not dependent on the mother, but will come to maturity if separated 

 from her. The eggs vary in number, old individuals laying upwards of forty. It has been calculated 

 that in one year a female would become the progenitor of 4,442,189,120 young, so that the abundance 



