20 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



larger bunches of eggs a gentle rotary motion ; but this caused the 

 smaller bunches and the free eggs to rise sometimes to more than half 

 the height of the jar and kept them quite strongly agitated. Although 

 the eggs are very hardy, and in nature, while attached to the swimmerets 

 of the parent lobster, are given but little motion, this greater activity 

 ai)pears to be essential to their well-being in the artificial hatching 

 apparatus, for without it they soon die. Such a fate befell most of one 

 lot contained in a McDonald jar, through which but a gentle current 

 was allowed to i)ass, and in one of the hatching-boxes, where the sup- 

 l)ly of water was very much greater, though distributed over a much 

 larger surface, so that no motion was given to the eggs, they all died 

 inside of a week. The accumulation about the eggs of impurities from 

 the water may have been the principal cause of this mortality; but as 

 the eggs are well able to endure active motion and thrive best in a 

 strong current, there can be no objection to pursuing that method. An 

 illustration of the hardy character of the eggs is furnished by the fact 

 that a small quantity left over night in a watch glass of sea water were 

 alive and apparently in good condition in the morning, although the 

 density of the water had been greatly increased by evaporation. 



The chief annoyances to hatching work at the Wood's HoU station 

 this summer were, first, iron rust, and, second, sediment from the har- 

 bor. The supply mains in use when the laboratory was first opened 

 consisted of iron pipes without a protective lining; they had been down 

 a year, and gave off such a large quantity of rust, which often ap- 

 peared as a dense reddish cloud of exceedingly fine suspended particles, 

 that the hatching-jars would become strongly stained inside of a few 

 hours and the eggs themselves become perceptibly coated. After the 

 cement-lined pipes had been substituted, this trouble ceased for the 

 most part, but a great deal of sediment was observed in the sea water 

 the remainder of the season, and notwithstanding the strong current 

 passing constantly through the jars, a very perceptible deposit was 

 formed over the lower-lying eggs in the course of every twelve hours. 

 The lighter particles of sediment also collected to a large extent on the 

 sides of the jars and tubing, and often adhered to the more buoyant eggs. 

 Cloth filters were used to strain out these impurities, but they proved 

 unsatisfactory, and the course finally pursued was to force out the sedi- 

 ment every morning and evening by momentarily increasing the flow 

 of water to its utmost capacity, and then shutting it off', repeating this 

 oi^eration at frequent intervals for several minutes. The effect was 

 thoroughly to stir up the sediment, which, being lighter than the eggs, 

 remained longer in suspension and was carried off" when the flow was 

 again made normal. The eggs were transferred to clean jars every four 

 or five days, and the old jars thoroughly washed. 



By constant attention to all these details, the eggs were kept in a 

 healthy and tolerably clean condition as long as the experiments were 

 kept up. A neglect of these precautions always resulted in the de- 



