3IO BULLETIN OF THE BUREAU OF FISHERIES. 



eggs did not hatch in the jars, since they could not be prevented from adhering to each 

 other in masses, and they soon died. 



The effects of changes in temperature of the water on hatching were observed. 

 The highest temperature at which thejarvae were observed to hatch normally was 78 ° F. 

 The temperature of the water fluctuated considerably during the day, the range being 

 from 76 to 98 ° F. The changes often occurred abruptly and marked the death of many 

 larvae. Many of the eggs did not hatch at 98° F., and the larvae which did emerge at the 

 higher temperatures usually died before becoming entirely free of the egg membrane. 



It was observed that the temperature of the water fluctuated less during the night, 

 especially when the tide was rising, and it remained not far from 76 F. It was inferred 

 from this that the temperature offshore was not far from 76 F. It, therefore, does not 

 seem probable that hatching takes place in shallow water where the temperature con- 

 ditions apparently either inhibit the hatching of the eggs or cause the larvae to emerge in 

 a weakened condition. It is known that the phyllasomes of closely related species have 

 been taken in 75 fathoms of water far offshore. 



The embryo about to hatch is much compressed within the egg membrane, and it 

 is colorless and transparent except for the black eyes and bright yellowish red dot of 

 unabsorbed yolk, which are opaque. It was found necessary to reduce the flow of water 

 in the jars at this stage, because the embryos are buoyant and hatch as they float 

 upward. The larva emerges much doubled up, like a fleck of cotton waste, but quickly 

 straightens out into the normal position and at once begins to move about actively. 



The first-stage larva (Fig. 273) is a phyllasome which is a modification of the mysis 

 or schizopod larva of other Macrura, such as the northern lobster, but the subsequent 

 development is by no means the same. The short embryonic development predicts a 

 long larval development which may render artificial propagation a very difficult problem. 



No cannibalistic tendencies were noted among the larva;, but plenty of space should 

 be provided, to prevent their appendages which are long and provided with numerous 

 spines and setae, from becoming closely entangled with those of other larvae. This 

 danger is especially great unless the light is diffused, since the larvae are decidedly helio- 

 tropic. They become massed together and must be separated by means of some stirring 

 device. Silt suspended in the water becomes lodged on the setae and spines of the larvae 

 and weights them down to their death. Feeding was attempted, but the results were 

 negative. The food of the larvae is probably other plankton, and any method that can 

 be devised to increase the growth of these organisms will greatly aid the solution of a 

 difficult problem. 



