188 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Surface towing was done at the following places in the same year without obtain- 

 ing any lobsters: August 1, 17, and IS, Vineyard Sound; August 23, off Cuttyhunk; 

 August 27, 30, 31, Woods Hole Harbor. 



Professor S. I. Smith says of the young lobsters which he obtained in Vineyard 

 Sound in the summer of 1871, that numerous specimens "were mostly taken at the 

 surface in the daytime, either with the towing or hand net" (182). Of the older pelagic 

 stages he says: 



They appear to live a large part of the time at the surface, as in the earlier stages, and were often 

 seen swimming ahout among the surface animals. They were frequently taken from the 8th to the 28th 

 of July, and very likely occur much later. 1 



We know that lobsters are now far less abundant around the Elizabeth Islands 

 than they were twenty years ago, and we should expect to find that the young had 

 diminished in a proportionate degree. Millions of larvae, however, must still be 

 hatched in Vineyard Sound and adjacent waters every year. What then becomes of 

 them? I believe that they are eaten up by surface-feeding animals, principally fish, 

 or meet their death from indiscriminate causes. The tides tend to disperse the young 

 over a wide area, thus carrying them to and from the shores. Horizontal distribution 

 alone would not account for the extreme scarcity of the young in Vineyard Sound at 

 the present time. If, however, there were a corresponding vertical distribution, the 

 conclusion which we have reached would not be warranted. It thus becomes a matter 

 of much interest to determine the heliotropism of the larva?, or the law which governs 

 their vertical movements in the water. 



The results of my observations and experiments with larva? lead me to conclude 

 that the young, free-swimming lobster usually displays what Loeb has called positive 

 heliotropism (125) — that is, it tends to swim toward the light or near the surface iu the 

 daytime. The conclusion therefore which we stated above, that the absence or extreme 

 scarcity of young lobsters in a region where the adults still abound is due to their destruc- 

 tion, is supported by experimental testimony. The bearing of this fact upon the artificial 

 propagation of lobsters I have discussed in an earlier paper (see 97). 



I will add a few notes upon the experiments which were made to test the helio- 

 tropism of these larva?. 



Experiment 1. — On June 27, 1894, 1 placed about 25,000 young lobsters, in the first 

 larval stage, in the observation pool at the Fish Commission Station, to watch their 

 behavior. The sun was intermittently obscured by clouds during the greater part 

 of the forenoon. When liberated, the larva? formed a large cluster near the surface, 

 where they remained for a short time. Then all went down to a distance of from 1 

 to 2 feet, some apparently reaching the bottom, a distance of 3 feet more. A lot of small 



'With reference to this subject, Professor Smith has kindly written in detail substantially as 

 follows : "All the larva 1 captured in Vineyard Sound and neighborhood in 1871, on which my papers 

 were based, were taken in the 'daytime.' My notes usually give only 'day,' or 'evening' for time 

 of capture, but the larvae of my first and second stages, taken July 1, are marked 'forenoon.' 

 Since 1871 1 have many records of first and second stages taken in the 'day' and, as far as I can find 

 now, only two cases of capture in the 'evening,' and one of these cases was when the electric light 

 was used in the water to attract the surface forms. The young in the adult form [equivalent to fourth 

 and possibly fifth and sixth stages described in this work] were, however, often taken in the evening 

 and were almost always attracted by the electric light. In my experience the young of the adult 

 form were much more frequently taken at the surface than the larvae." 



