LOBSTER INVESTIGATIONS 55 



SESSIONAL PAPER No. 38a 



following depths of water, 21 inches, 22, lY, 20, 17, 19, 19, 23, 24, 26, 24, or an average 

 of 21 inches, in which to float our apparatus. It can scarcely be expected that an 

 apparatus, which requires at least 10 feet of water in which to operate, can be made 

 to operate successfully in a depth of 21 inches. 



FIRST HATCHING. 



Our first hatching began July 12, and in two days we had about 40,000 larvne in 

 the four boxes. While only an odd diatom could be found on the fry during the first 

 day, large numbers were visible by the fifteenth. As the diatoms increased, the fry 

 became "fu2zy" to the naked eye. Both last year and this the effect of the diatoms 

 was largely, if not solely, mechanical. Feeding was interfered with, the animals 

 became exhausted with the effort of swimming, sank to the bottom, and soon died. 



The remarkable thing about this mortality was that last year it was caused by the 

 diatom Synedra investiens, whereas this year it was caused by Licmophora Lyngbyei. 

 Why the principal destructive organism should have been different in the two years is 

 difficult to understand, unless it were due to the fact that in 1914 the sea-water reach- 

 ing our boxes came through the sand, gravel, and mud of the sea-wall, whereas, in 

 1915 it came through an earthenware pipe from the open sea. 



As soon as it became apparent that this season's fry were likely to share the same 

 fate as those of last year, the contents of two of the boxes were transferred to St. 

 Mary's bay, in order, if possible, to save their lives. Meanwhile the leakage steadily 

 grew worse. On the 19th the average depth of water below the boxes was only 10' 

 inches. As a result, good ventilation became impossible, because the water drawn in 

 through the bottom windows gradually became muddy. It was resolved, therefore, 

 not to use more than two boxes for rearing purposes for the remainder of the season. 

 The other two were fitted up with shelters, or nests, for adult lobsters, so that more 

 accurate observations could be made upon them than was possible in the compartments- 

 of the pound. 



DETENTION DEVICES. / 



It should, perhaps, be explained that we employed five different devices, or enclo- 

 sures, for impounding adults. The smallest was the crate, about 3 feet by 2 feet by 

 2 feet, which floated on the water, and could be used for temporary purposes only. 

 The second was our rearing boxes, 10 feet by 10 feet by 2i feet, with revolving paddles 

 inside, so as to aerate the water, as described in the report of last yearl The third 

 was the compartment, 20 feet by 10 feet by the varying depth of the water at high and 

 at low tide. The wooden slats of which it was constructed were only about 4^ feet 

 high. As can be seen from the illustration, there were six of these compartments 

 within the cement pound. The fourth enclosure was the pound, and the fifth, tihe 

 pond, but these two latter were so large that is was impossible to use them for observa- 

 tion purposes. The compartments could be used for observation purposes only at low 

 water. The real purpose of their construction was to serve as sub-divisions of the 

 pound, in which lobsters could be kept for experimental and observational purposes. 



FAILURE. 



We had even worse luck this season than last. Of the 20,000 fry which we tried 

 to rear in the two remaining boxes, beginning July 12, only twenty-one remained 

 alive on the 30th of July, and they were all in the second stage of development. Not 

 one had moulted a second time, and they had taken thirteen days before mo;ilting even. 



38a— 5J 



