190 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



THE MORTALITY OF LARVAE. 



The following notes illustrate the difficulty of raising the young of the lobster 

 in close quarters. Old eggs were always placed in the jars, but even when the water 

 was agitated so that these were floated, the young invariably preferred to feed on one 

 another. The death rate, however, is due in part to other causes besides cannibalism. 



On July 2d, 1893, 130 larvae in the second stage were placed in a 4-gallon jar and supplied with 

 running water. On July 3d, 108 were alive ; on July 4th, 96 ; July 5th, 89, 3 of these in the third stage ; 

 on July 6th, 63 were alive, 47 of these having molted for the third time. In the course of four days 

 48 per cent had succumbed. 



On July 1st, 100 second larva; were placed in a hatching jar. On July 2d, 82 were living; July 

 3d, 73; July 4th, 64, 2 of these having molted to the second stage; and on July 5th, 50 were alive, 24 

 in the third stage. The third larvae, 26 in all, were left in this jar, and on July 6th 24 were alive; on 

 the following day only 6. 



June 29th, 1893, 1 placed 12 lobsters in the first larval stage in four flat glass dishes (3 to a dish). 

 By the 1st of July 10 were alive, 4 in the second stage; on July 5th 7 were living, all in the second 

 stage, and July 6th 1 second larva only was alive. 



July 6th I placed 6 iirst larvae in two flat dishes (3 to a dish) with lobster eggs for food. Each 

 lobster was 8 mm. long. On July 7th 2 in one dish were alive, both in second stage and devouring 

 the remaining larva; no change in the other dish. On the 9th, at 9 a. m., 4 were alive, 3 in the third 

 stage and 1 in the first. 



I placed 4 third larvae in a hatching jar on the 7th of July. All were living on the 13th, and on 

 the 15th 3 were alive, having molted to the fourth stage. The smallest had been attacked by the rest 

 and its thoracic legs were eaten off. I left 2 fourth larvae in the jar, both of which were in the fifth 

 stage on the 27th of the month. 



THE EFFECT OF INCREASED TEMPERATURE ON THE RATE OF DEVELOPMENT 



OF THE LARViE. 



The following experiment is interesting in showing how the rate of development 

 is affected by raising the temperature : 



July 1st, 1893, I placed 100 first larvae of the lobster in a hatching jar, with food, and heated the 

 water by means of a block-tin coil to 74° F. The water in the aquaria at this time registered 66.9° 

 and that of the harbor 66°. 



July 2d, 9 o'clock a. m., 56 were alive. Some were weak and lying on their backs at the bottom, 

 an easy prey of the strong. 



July 3d, 9.30 a. m., 56 alive, not looking healthy, many with air bubbles in branchial cavities; 

 temperature raised to 78°. 



July 4th, 41 alive, 28 in second stage, 13 in third stage. 



July 5th, 24 alive; left third larvae, 18 in all, in jar. 



July 6th, 7 alive; temperature of water 80°. 



July 7th, all living, another in fourth stage; left 6 third larva? in jar. 



July 8th, all alive, 3 molted to fourth stage. One fourth larva had one blind eye; the eye was 

 small and pigment deficient. All left in jar. 



July 11th, all alive, 4 in fourth stage, 2 in third stage. 



July 13th, all alive; no change; temperature 79°; left 3 larva; in fourth stage in jar. 



July 15th, 2 alive. 



July 17th, both living; temperature 79°. 



July 19th, both living; temperature 78 c . 



July 21st, both living; temperature 75°. 



July 30th, one alive; temperature 78°. 



August 2d, one alive, in fifth stage (length 13 mm.) ; temperature 79°. 



August 5th, last one dead. 



We see that with a rise in temperature of from 7 to 13 degrees the third molt was 

 passed in about 5 days, which is not far from the average age of these larva? reared 



