38 



cult to explain. It is a problem which may be recommended to 

 the physiologist. 



It is evident from the table and the diagram that this specimen 

 when captured was not a product of the year of capture. It is 

 probable, indeed, that it was then not less than two years old, 

 and we have again therefore a valuable instance of the long life 

 of even the smaller types of Decapods. 



An attempt may now be made to present the growth of the 

 lobster, Homarus vulgaris. The spawning season may be said 

 to be July to September, and the hatching season, June to August, 

 but occasional cases are obtained of hatching taking place as late 

 as October. When hatched the larva possesses all the appendages 

 fully developed to the last thoracic, and the abdomen is segmented, 

 the telson being prolonged into forks, and the dorsal walls of the 

 abdominal segments into spines. A larva with this structure 

 cannot be called a protozoea: it is a zoea. It moults almost at 

 once, giving a zoea in which the pleopods 2-5 are developed. At 

 the next ecdysis the uropods are added. The limbs are practically 

 completed at the fourth stage, but as a more conspicuous change 

 takes place at the next ecdysis, and a change of habit leading from 

 the pelagic to a more demersal life the term megalopa is more 

 conveniently reserved for that stage which here and in America 

 is now generally distinguished as the lobsterling. Still further 

 ecdyses take place before the last vestiges of the exopods disappear 

 from the jDereiopods. 



The four zoea stages last from about three weeks to a month 

 or longer according to temperature. The lobsterling is still to 

 some extent pelagic, but it periodically comes to rest at the bottom, 

 taking advantage of the shelter provided. 



The lobsterlings measure from 1-6 to 1-9 cm., and have been 

 found in our tank experiments at CuUercoats from about the end 

 of July to September. A size of 3*5 cm. may be reached by the 

 end of September, and of 5 cm. in November. On the other 

 hand, we have examples which in the following July were only 

 5-4 to 6-6 cm. With this as an introduction the material upon 

 which an estimate of the growth is based may be presented. 

 (Table VII.). 



