40 REPORT OF NEW JERSEY STATE MUSEUM. 



liarly modified nephridia, formed either like shell-glands opening- 

 on second maxilla or antennary (green) glands opening on an- 

 tenna. Nervous system consists of brain united by oesophageal 

 connectives with ventral nerve-cord, formed of double chain of 

 ganglia joined together by commisures and connectives. First 

 three pairs of embryonic ganglia commonly unite to form brain, 

 which therefore syn-cerebrum. Sexes separate or united, sexual 

 dimorphism comimon, and parthenogenesis frequent. Sperms 

 usually non-motile, and eggs usually centrolecithal, sometimes 

 telolecithal, or almost alecithal. Muscles striped, and no cilia. 

 Segmentation of oosperm usually superficial, but may be com- 

 plete or discoid. Embryo passes through nauplius stage, which 

 may be free-swimiming larva or may be passed through before 

 hatching, and characterized by three pairs of appendages, which 

 form into antennules, antennae and mandibles of adult. 



The Crustacea are thus seen to form a very great assemblage 

 of animals as here understood. The group Xiphosiira, or king 

 crabs as they are commonly known, are now usually admitted 

 with the Arachnida. The Crustacea agree with them, however, 

 in that both typically breathe in water by means of gills joined 

 to the appendages. The absence of antennae will serve to dis- 

 tinguish the king crabs at once, and in this character they share 

 alike with all the other Arachnida. 



The ethology has been summed up very comprehensively by 

 Messrs. Parker and Haswell, from which the following is largely 

 extracted. Crustacea are remarkable for their very perfect 

 adaptation to the most various conditions in life, occuring in the 

 fresh waters, in the sea, in brine pools, in subterranean caves and 

 on land, throughout the globe. Many of those living in the sea 

 are littoral, others pelagic, and some abyssal, descending in the 

 depths of the sea over three thousand fathoms. Certain copepods 

 (as Pontellina) are said to be almost aerial, leaping out of the 

 water or apparently flying in similar fashion to the flying fishes 

 or exocoetids. Solitary forms are found in such types as the 

 lobsters, crawfishes, etc., while the contrary is seen in the im- 

 mense shoals of shrimps. Most Crustacea prey on living animals 

 or devour carrion. In the case of fixed forms, like the barnacles, 



