INVERTEBRATE ZOOLOGY. 105 



the adults. A Nani)lias is oval in form and possesses three pairs of 

 appendages nsed as legs. In later development these become the 

 first and second antennae and mandibles, vrhile new somites and 

 appendages api^ear posterior to the original three, and develop into 

 the remainder of the body. 



[ 76. Parasitic CopeiMcla. Many members of this group have forsaken their independent 

 existence and are found as parasites upon the gills or external surface of aquatic verte- 

 brates, representing all stages of degeneracy. Open the ojjerculum or gill-flap of any fish, 

 marine or fresh water, and search among the reddish fringes (gills) for these forms. Some 

 are irregular, almost shapeless masses, tubular or sac-like, while others still show more or 

 less affinity to Cyclops. Even the most degenerate possess the lateral egg-sacs which, how- 

 ever, may appear as close coils of tubules. When found, cut away the portion to which they 

 are attached, wash until clean and examine with lens. Ascertain mode of attachment, look- 

 ing especially for hooks, burrs, or other parts used in clinging to their host. Are these mod- 

 ifications of typical parts, or new formations ':] 



Type XIV.- Simocephalus Sp ? i^n- other typical Branchiopod). 



77. General anatomy. The general structure may be ascertained from 

 living specimens placed under a cover-glass. They lie iipon their side and are 

 fiat and transparent, giving one the opportunity of using the higher lens. For 

 mode of motion, shape as seen from above, etc., they must be studied in a 

 watch-crystal. 



(a) External anatomy. The .shell is formed by an integumental duplica- 

 ture, that is, it is an exaggeration of a lateral fold. Focus on its 

 surface for peculiar markings upon it. The head is free and provided 

 with a short beak, the rostrum. The abdomen is slender and with- 

 out appendages. It moves rapidly back and forth, being capable of 

 projecting from beyond the margin of the shell. It is tijiijed with a 

 pair of curved terminal si)ines, above which is a row of smaller 

 spines. It is generally held in a ciirved position along the ventral 

 side. The eye is median (its true position being seen in a dorsal view) 

 and consists of a mass of black pigment, surrounded by highly re- 

 fractive bodies, the " crystalline lenses." The eye is moved by minute 

 muscular bands. There are two pairs of antennae, a short anterior 

 pair, near the rostrum, provided with knobbed olfactory hairs, and 

 an enormously developed second pair, the oar-antennae. These pos- 

 sess two branches, one of four and the other of three joints. They 

 are used for locomotion and thus functionally replace the legs which 

 bear gills and are used solely for respiration. These legs are seen 



