NATURAL HISTORY OF AMERICAN LOBSTER. 157 



body. With its egg cluster on its back Gonodactylus stands or sits on guard at the 

 mouth of the burrow, awaiting its prey, and meantime keeping its eggs aerated by the 

 farming movements of the swimmerets. Says Professor Brooks: 



When the burrow is broken open she quickly rolls the eggs into a ball, folds them under her body 

 in a big armful, between the large joints of her raptorial claws, and endeavors to escape with them to 

 a place of safety. The promptness with which this action is performed would seem to indicate that 

 it is an instinct which has been acquired to meet some danger which frequently presents itself. 



The decapods have the general characteristics given for the lobster in chapter vi. 

 All glue their eggs to their swimmerets and carry them thus attached, protecting and 

 aerating them for a period of weeks or months with unerring instinct until they hatch. 

 After pairing, the sexes frequently separate, as is possibly the case with lobsters (see p. 

 302), or they remain together, swimming side by side, and receiving mutual aid as in 

 Stenopus, for as long at least as the period of fosterage lasts. The young, upon hatching, 

 usually either swarm together for a time, or are immediately dispersed, as in the lobster. 

 A long and perilous metamorphosis awaits the young of most of the decapods, during 

 which they are pelagic or free surface swimmers, but every_degreeof_abbreviation of . this 

 development exists, and in the crajrfishes and certain other species, both fluviatile and 

 marine, the young resemble the parent at birth, and a complex family life, which wUl 

 receive attention later, may be developed. 



The decapods are divisible into three intergrading suborders: (i) The Macrura, 

 or long-tailed Crustacea like the shrimp and true lobsters; (2) the Anomura or hermit 

 lobsters and hermit crabs, and (3) the Brachynra or true crabs, the most highly special- 

 ized of the entire class, in which the tail is not only very short but is even rudimentary 

 in the male. 



To follow out the Macrura only and in brief, they embrace numerous families 

 possessing both zoological interest and economic value, of which the most important are 

 (i) the Nephropsidae (Astacidae of many authors) or true lobsters; (2) the fresh-water 

 crajrfishes of the world, or Astacidae of North America and Europe, and the Parastacidae 

 of the Southern Hemisphere; (3) the other decapods known collectively as prawns or 

 shrimps, including the Peneidae, Alpheidae, Pandalidae, Crangonidae, and Palaemonidae ; 

 (4) the Palinuridae, variously known as spiny, thorny, or rock lobsters, and (5) the Scyl- 

 laridae, which are sometimes classed with the Galatheidae, and are known as warty lobsters. 

 Representatives of some of these families will now be briefly considered, before dealing 

 more fully with the special subjects of this work embraced in the family of Nephropsidae. 



The crayfish (of the family Astacida) has become a favorite subject in zoology, 

 and very few invertebrates have received the degree of attention which naturalists have 

 paid to every phase of its history. It is well known that the common crayfish, Astacus 

 fluviaiilis, has been used for centuries as food all over the continent of Europe, while 

 in France the farming of crayfish in order to increase the natural supply of this crus- 

 tacean has been successfully practiced for some time. For many years also crayfish 

 have found their way to the markets of American cities which possess large populations 

 of foreign birth, as New York, New Orleans, Chicago, Milwaukee, and San Francisco; 

 but many persons would probably be surprised to learn the present status of the cray- 



