232 Phylum Arthropoda 



prevent this and partly to aerate the water each tank was fitted with a 

 large funnel covered with muslin and with a tube leading to the bottom 

 of the tank. Into each funnel a small but steady stream of water splashed 

 from a tap about a foot above. When the larvae began to hatch a series 

 of nursery tanks made of battery jars were fitted up in a similar manner 

 and a few large beakers were also used. 



It was found necessary to have the eggs carried until hatching by the 

 females, as larvae were never successfully hatched from eggs that had 

 become separated. Ovigerous females were taken with a small beam 

 trawl on various grounds sometimes 50 miles away or more. During 

 transportation to the station they were carried in a large galvanized tub 

 with changes of water at least every hour. They were placed in the big 

 tanks and kept there until their eggs had hatched. During their cap- 

 tivity they were fed mainly on chopped crab's liver and marine worms. 

 Most of them kept healthy although some of those from deep water 

 acted as if they were blind and bruised themselves badly against the 

 sides of the tanks. 



In many cases the larvae appeared to be healthy for a week or ten 

 days and then died before molting. A few Pandalus danae larvae reached 

 the second stage but none of the others ever succeeded in passing the first 

 molt (although Spirontocaris and Crago larvae were easily reared in 

 beakers through several stages). 



The salinities in the tanks compared favorably with the natural ones. 

 Moreover no sudden ill effects were noted on the days that the salinity 

 dropped and experiments conducted in the laboratory had indicated 

 that the adult shrimps at least could stand a fairly wide range of salinity. 



The pH of the water in the tanks remained close to that in the sea 

 near the station. 



As the adult shrimps all came from comparatively deep water (20 to 

 60 fathoms) they were subjected in the tanks to much lower pressures, 

 and perhaps in some cases to stronger light than normal although the 

 latter was kept subdued. The adults, however, appeared healthy during 

 hatching. The larvae occur naturally from a depth of about 4 fathoms to 

 the bottom, the younger stages keeping nearer the surface. It does not 

 appear probable, therefore, that light or pressure were adverse factors in 

 the rearing of the larvae. 



The larvae were given various foods — eggs of marine worms, plankton, 

 and finely minced crab liver. Apparently they ate the food, as traces 

 could be found in their alimentary tracts. Examination of larvae ob- 

 tained in plankton hauls indicated that they had been feeding on the 

 smaller plankton organisms. It is quite possible that unsuitable food was 

 one of the chief adverse factors. 



