THE AMERICAN LOBSTER. 225 



molt rudimentary abdominal appendages appear on the second to fifth abdominal 

 somites, inclusive, and the branchial formula is completed. 



(5(5) At the fourth molt it loses the use of its larval swimming organs, but still 

 remains at the surface, propelling itself forward by its swimmerets and backward by 

 flexion of the abdomen. It is now from three to four weeks old, is half an inch long, 

 and has characteristic colors. 



(57) After the fifth molt is passed the young lobster still swims at the surface, 

 though it is possible that some leave it during this stage. When the sixth stage is 

 reached, age five to six or eight weeks, length about three-fourths of an inch, it remains 

 at the surface for a time at least, but goes to the bottom to stay before the seventh 

 molt is passed. At the sixth molt all trace of the larval swimming organs is lost. 



(58) The molts follow each other at rather short intervals, and during the first 

 year of life, supposing the animal to have been hatched in June, the lobster molts 

 from fourteen to seventeen times and attains a length of from 2 to 3 inches. The 

 main facts of the subsequent life-history need not be repeated. 



(59) The problem of artificial propagation of the lobster will be solved when 

 means are devised by which the larva? after hatching can be reared in large inclosures 

 until the fifth or sixth stage, when they are able to take care of themselves. 



(60) Food of larva;. — The food of the larval lobster consists of minute pelagic 

 organisms of all kinds. They show little discrimination at this time, snapping up any 

 floating objects not too large for them to manage. 



(61) Heliotropism of larva;. — In the pelagic stages the young lobsters are positively 

 heliotropic, rising to the surface in the daytime and staying there, and going down at 

 night. This habit is not invariable, but the capture of the young by day is the rule, 

 by night the exception. 



(62) Survival of larvw. — Great destruction is wrought upon the free-swimming 

 stages by both animate and inanimate enemies. A survival of 2 in every 10,000 

 larvae hatched would maintain the species at an equilibrium, and the destruction of 

 the young under the present conditions of the fishery is probably even greater than 

 this implies. (For a discussion of this subject see No. 97 of Bibliography.) 



(63) The general scarcity of the young in the hatching season in places known to 

 abound in lobsters is due (1) to their wide horizontal distribution, and (2) to their 

 destruction. 



(64) The whole course of development and later growth is slow. The slow larval 

 development secures the necessary transportation from the shores and wide horizontal 

 distribution, which is absolutely necessary for the life of the species. An abbreviated 

 metamorphosis such as is found in this animal appears to be a compromise between a 

 still longer development which the animal would have to go through if the egg 

 possessed less yolk, and the limitations to protoplasmic activity which are imposed by 

 the temperature of the North Atlantic Ocean. 



For the facts pertaining to the development of the embryo the reader must refer 

 to Chapter xiii, and for details and the discussion of general questions to the body 

 of the work. 



F. C. B. 1895—15 



