ARTHROPODA. 



291 



of ten or eleven months. After hatching the young undergo a series -of 

 moultings during which time they are the prey of many kinds of enemies. 

 Such is the mortality that on an average, two out of an entire spawning 

 do not reach maturity. Two general methods have been tried to make 



FIG. 131. 



FIG. 131. Palamonetes vulgaris. From Verrill. 



Questions on the figure. Compare the appendages of Palaemonetes 

 with those of the lobster, the crab and Gammarus. What seem to be the 

 functions of the various appendages, so far as position and form may 

 indicate? 



FIG. 132. 



FIG. 132. Gammarus ornatus. From Verrill. 



Questions on the figure. How does this form compare with the 

 lobster and the crabs in differentiation of the segments, in fusion of the 

 segments and in the differentiation of the appendages? 



good the decline in the supply : first, legislation forbidding the taking of 

 animals under the size which indicates sexual maturity (eight to twelve 

 inches), and forbidding the capture of females carrying the developmg 

 embryos ; and, second, attempts on the part of the national government to 

 hatch artificially and care for the moulting young under such conditions 

 that they will be protected from their natural enemies. The problem is 



