BULLETIN OF THE BUREAU OF FISHERIES. 
162 
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 country has been mainly developed during the last hundred years. The same 
gradual falling off 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 will weigh more 
than the European form. (See chapter in, 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 until 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 
several millions, as in Callinectes and Palinurus, and from nearly \ inch, in certain deep 
sea shrimp, to less than T jjo 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 
life 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 under 
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 accumulation 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 biennial, but it is possible 
