ENTOMOSTRACA. QTT 
the body, forcing the water into the brood-cavity, and again 
expelling it through a wide orifice. These root-barnacles 
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- 
‘Fig. 230.—Saceulina car- tion, while another form (a species of 
cini, natural size. a, base 
Bt rout! &, opening for exit Peltogaster ?) also leaves the egg in the 
of e 28. — rom Brehm’s pupa form. 
Thierleben. 
Order 2. Entomostraca (Water-fleas). 
—The type of this group is Cyclops (Fig. 231, C. serru- 
latus F. see also Fig. 232) in which the el is pear- 
shaped, with a single bright eye in 
the middle of the head ; two pairs 
of antennex, used for ayimiming 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 , Fig. 231.—Cyctops. ¢, eye, 
aborted, while the body increases aa ee ie 
greatly in size. Such are the fish-lice, represented by the 
Lernea of the cod. 
