l62 BULLETIN OF THE BUREAU OF FISHERIES. 



of such structures. In fact, either one, two, or three spines of inconstant size may be 

 present in the American lobster, though this is a condition which in some cases might 

 be attributable to an injury and its imperfect repair. In the slight differences observed 

 in the development of the American form, however, there are more valid reasons for 

 maintaining the specific names. 



It has been the accepted belief that the American lobster attains a greater size than 

 its European counterpart, but it is possible that in early days the maximum size was 

 essentially the same. The fishing of lobsters in Europe is of great antiquity, and the 

 average size of the adults taken has been reduced in consequence, while the industry in 

 this cotmtry has been mainly developed during the last hundred years. The same 

 gradual faUing oJBf in size, due to the same cause, has nevertheless been experienced 

 on the New England coast and in the maritime provinces. It seems certain, however, 

 that the American lobster has larger claws, and, length for length, it wiU weigh more 

 than the European form. (See chapter iii, p. 195.) 



The slight differences in the development of the two forms, already referred to, are 

 seen in the young at the moment of hatching. The abridgement of the larval period 

 has been carried a step farther in the common lobster of Europe, so that its young issue 

 from their eggs in a stage nearly comparable to the second larva of the American lobster. 



DEVELOPMENT OF THE CRUSTACEA. 



All the decapod Crustacea are developed from eggs which in the Macrura are fertilized 

 outside of the body and are generally carried imtil hatched on the under side of the tail 

 or abdomen of the female, where they are glued to certain hairs of the swimmerets. 

 The sperm cells are vesiculate and often "rayed." The eggs vary in number from less 

 than a dozen, as found in small species of Synalpheus with abbreviated development, to 

 severaJL millions, as in Callinectes and Palinurus, and from nearly \ inch, in certain deep 

 sea shrimp, to less than yf^j- inch in diameter. 



The time of fertilization, so far as known, always coincides with that of oviposition 

 and attachment. By means of a liquid cement the eggs are fixed, in a way to be later 

 discussed, often to one another and always to the swimmerets under the abdomen. In 

 Ufe the swimmerets beat rhythmically backward and forward, whether the animal is in 

 motion or at rest, and the attached eggs are thus constantly cleaned and aerated imder 

 natural conditions. 



The ova are delicate and soon die if cut loose and left to themselves. In order to 

 rear them successfully under such conditions, artificial aeration of some kind must be 

 resorted to and conditions devised to prevent the accmnulation of sediment or parasitic 

 growths over the surfaces of the eggs. The best "brooder" of any decapod's eggs is 

 undoubtedly the mother, whether lobster, shrimp, or crab. 



The period of fosterage varies from a few days or weeks in some of the smaller 

 tropical decapod Crustacea to nearly a year in the lobsters. There is a similar variation in 

 the frequency of spawning; certain Alpheidae of the Bahama Islands apparently have a 

 succession of broods the year round, while others may lay their eggs twice or once only 

 each year. In the American lobster the breeding period is bieimial, but it is possible 



