ENTOM08TRACA. 



27? 



Fig 



?s. From Brehm's 

 eben. 



the body, forcing the water into the brood-cavity, and again 



expelling it through a wide orifice. These root-barna.cles 

 recall the Trematode worms, though the 

 latter are much more highly organized. 

 An allied form (Cryptophialus minutus) 

 undergoes the larval or Nauplius stage 

 in the egg, hatching in the pupa condi- 

 -saccuiina car- tion > while another form (a species of 

 PMoffosterf) also leaves the egg in the 

 pupa form. 



Order 2. Entomostraca (Water-fleas). 



The type of this group is Cyclops (Fig. 231, G. serru- 



latus F. see also Fig. 232) in which the body is pear- 



shaped, with a single bright eye in 



the middle of the head ; two pairs 



of antennae, used for swimming as 



well as sense-organs ; biting mouth- 



parts, and with short legs. The 



sexes are distinct, the females swim- 



ming about with two egg-masses 



attached to the base of the ab- 



domen. The young is a Nauplius, 



much like that represented in Fig. 



229, the mouth-organs, the legs 



and abdominal segments arising 



after successive moults, until the 



adult form is attained. Allied to 



Cyclops is Canthocamptus caver- 



narum Packard (Fig. 233), an eyed 



species, living in Willie's Spring, in 



Mammoth Cave. 

 Many Entomostraca are parasitic, 



and consequently undergo a retro- 



grade development, losing the 



jointed structure of the body, the 



appendages being more or less 



aborted, while the body increases 



greatly in size. Such are the fish-lice, represented by the 



Lernaa of the cod. 



Fig. 231. Cyclops, e, eye , A. 

 heart; eg, eggs; /, feet. After 



