of the Fishery Board for Scotland. 



71 



Larvae — General Description. 



The zoeas are beautifully coloured in two predominant tints. On the 

 dorsum, in the gastric region, the double luminous blue spot is con- 

 spicuous. Then generally all over they are pigmented blue on the dorsum 

 of the thorax and abdomen, and yellow or red on the sides. Certain 

 zoeas, which to the naked eye have a slight bluish colouration, are seen, 

 on examination with transmitted light, to have a great quantity of yellow 

 pigment all over the body, the carapace, abdomen, and limbs, with the 

 dorsum of the thorax and of the abdomen blue. Others are to the naked 

 eye brilliantly coloured with dark red, which is seen by means of the 

 microscope to be distributed similarly to the yellow in the zoeas just 

 described. There are different shades of yellow : some lighter, others 

 darker. Occasionally the colouration shows to the naked eye a mixture 

 of red with bluish purple. In 1904 most of the lobster zoeas were red, 

 but others were green, showing no red to the naked eye. Some were of 

 a very pale green. 



The young lobster, while it is still a zoea, is, from its pelagic existence 

 during a period of at least three weeks, exposed to many dangers. Its 

 helpless condition, combined with its fairly large size, and conspicuous 

 colouration, will, no doubt, result in its extensive destruction. Its life 

 near the surface of the water will, however, give it, on the whole, probably 

 a better chance of escape from small fishes than if it were swimming 

 close to the bottom. 



While it is a zoea the lobster swims with its head bent downwards, 

 and it attacks the food usually from above. It sees a white piece of the 

 liver of the crab (Cancer pagurus) falling a good bit below it, and swims 

 down in a spiral till it reaches it. It, however, chases copepods on a level 

 with it, and also below it. When it is about to cast it seeks the bottom 

 of the box. Some which were put into a glass tank kept boring away 

 at the bottom in an endeavour to get down out of the strong light 

 apparently. 



The keen sight of the zoea is a remarkable contrast to the purblind 

 condition of the adult lobster. 



In the megalops stage the young lobster for the first time crawls. It 

 also swims, but now it swims forwards by means of its pleopods, with 

 the two long chelae held extended straight in front, in this way protecting 

 its rostrum from any rude shock which collision with an object might 

 produce. It also swims and floats in a manner similar to that known as 

 " treading water," when it tries to grasp anything near the surface, and 

 it turns round on its long axis after copepods at the surface of the water. 

 It can also dart backwards by means of a rapid stroke of its telson, after 

 the manner of the adult, but this in both stages usually follows surprise, 

 and is adopted for escape. It sinks whenever it ceases using its swim- 

 merets or telson. The megalops swims more than the later stages. It 

 seems to support itself more easily in the water than they do. Its 

 method of swimming is by means of its pleopods, that of a Crangon or 

 Palcemon. 



In this stage the antennas are short, and their length seems to vary a 

 little in different individuals. Certain megalopa have antennas which 

 reach just in front of the tip of the chela when it is stretched straight 

 out alongside the rostrum. Others have much shorter antennas. The 

 setose exopodites are only present in some of the examples of this stage. 



The megalops is the homologue of the sixth stage of Crangon vulgaris, 

 in that it has practically the adult characters, save for its very short 

 antenna?. It crawls about on the bottom of the box, and resists any wave 



