A PJiyllopod Crustacean. 91 



A PHYLLOPOD CRUSTACEAN 

 (Branchipus vernaUs) . 



External Anatomy. Observe the elongated body. Is 

 it distinctly segmented? Is it separated into a head, a 

 thorax, and an abdomen ? The appendages are leaf-like 

 (Phyllopod). They occur on which main division of the 

 body? Are they represented on the other regions ? Observe 

 the pair of flexible anterior antenna. In the males the 

 second antenna are enormously developed and form " clasp- 

 ing organs." Large at the base, each second antenna soon 

 becomes constricted, and forms an elongated chitinous rod. 

 Find the homologues of the second antennae in the female. 



The upper lip, lab rum, will be found as a median fold 

 extending posteriorly from between the bases of the second 

 antennae. Elevate the labrum and note that it covers the 

 jaws or mandibles. In what plane do the mandibles move ? 

 Are the cutting edges specially hardened? Note the open- 

 ing of the mouth. The maxillce, relatively poorly developed, 

 lie immediately posterior to the mouth. 



How many pairs of thoracic appendages are there ? Care- 

 fully remove one of the first pair, and note that there is a 

 basal portion, protopodite, which is extended distally by cer- 

 tain lobes. The internal lobe, endopodite, is the largest and 

 bears numerous seta along its inner and distal edge. Of the 

 same general structure is the outer lobe or exopodite, which 



