82 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



stages, it falls an easy prey to surface-feeding fish. The pugnacious instiuct of the 

 young larva', ami their remarkable activity in killing and devouring each other, inva- 

 riably attracts the notice of every one who watches them, and is an insurmountable 

 barrier to the successful raising of them in small aquaria. 



The young larvae are markedly heliotropic. If the vessel of water containing 

 them is placed in direct sunlight they immediately retreat to the opposite side of the 

 dish, that is, in the direction of the light rays or away from the source of light. If 

 the vessel is rotated through an angle of 180° the larvsB beat a similar retreat, and 

 this may be repeated a great many times. It is thus possible that the young free- 

 swimming stages of the lobster belong to that class of larvae which leave the surface 

 under the influence of sunlight and swim down to a considerable depth in the ocean, 

 rising to the surface again at night, but it is not known if this is the case, and it 

 may turn out that the young lobster both shuns and seeks the light, under different 

 conditions. This is a point for future experiment to decide.* During the past five 

 summers which I have spent at the IT. S. Fish Commission station at Woods Holl we 

 have used the towing net in various parts of Vineyard Sound on bright days, but 

 have never succeeded in capturing the first and second free-swimming stages. It 

 should also be added that but very few of these larvae were taken at night, and that 

 little towing was done after dusk. 



I believe that the scarcity of the young larvae of the lobster in the surface 

 waters of Vineyard Sound during the summer is due to the fact that they are eaten 

 up or otherwise destroyed. The survival of the young is probably much greater in 

 outside waters than in those sheltered by the land, which are so often the haunts of 

 surface-feeding fish. If this is the case, we may look upon the long free-swimming 

 period of the larvae as a means not only of securing a wide distribution, but also of a 

 transport from the shore. On the other hand, it is probable that the young lobster, 

 after its metamorphosis is finished, tends to move towards the shore, where it can find 

 a secure hiding-place among the rocks in shallow water. 



The fourth larva does not show the same kind of sensibility to light, and is fre- 

 quently taken at the surface on bright days. I have also dipped from the surface in 

 the daytime a few individuals in the third larval stage. At the fourth stage the larvae 

 have attained a length of about one-half inch, and have been taken in Vineyard Sound 

 as early as June 29 and as late as August 12, but the majority reach tins stage in from 

 fifteen to twenty days. Larvae have, however, been reared to the fourth stage in the 

 laboratory in eleven days. 



Larvae are never taken at the surface after the fifth stage, from which we infer 

 that they go to the bottom during this period and assume the habits of the adult. 

 At this time the difference between the large claws is not marked, and the first pair 

 of legs of the " tail " is represented only by miscroscopical buds. These and the 

 remaining adult characteristics are gradually assumed during successive molts. 



Very little has been known about the habits of young lobsters from LJto 3 inches 

 long. I am indebted to Mr. M. B. Spinney for a valuable collection of small lobsters 

 from the shores of Casco Bay and Small Point Harbor, Maine, which he has very care- 

 fully explored. Lobsters 3£ to 4 inches long were found quite often under rocks, 

 where at extreme low tide there would be an inch or two of water, but it was only in 



*See the jiaper by Dr. Loeb in thia volume, pp. (55 to 68. 



I 



