120 American Fisheries Society 



they are compelled to travel rapidly and this is accomplished by 

 means of the swimmerets alone. 



The real secret of their movements, however, appears to lie 

 in the changing salinity of the water and this probably affects 

 the animals by its varying osmotic pressure. At any rate, shrimp 

 seem by preference to remain in water of a more or less constant 

 salinity, or at least do not desire sudden changes and their migra- 

 tions into water of a different density is evidently comparatively 

 slow. With very young shrimp there is a slow gradual migration 

 inland and as these immature shrimp approach maturity there is 

 a second gradual migration, this time back towards the sea, where 

 they return when they reach the sexual stage and where they 

 appear to remain for their entire adult life. 



The breeding season does not seem to be a short one and varies 

 with the individual shrimp, apparently being extended over a 

 considerable period which covers at least the spring, summer and 

 early fall months. As our work was handicapped last winter 

 during the influenza epidemic, it will take further observations to 

 determine the entire extent of the breeding period and the per 

 cent of individuals spawning throughout the various seasons. 

 This more or less extended breeding period is sufficient to account 

 for specimens of all sizes being found over a considerable portion 

 of the year. Because of the difficulty of keeping adult specimens 

 in captivity, no observations have as yet been made upon the 

 spawning habits of this species. There is no doubt that in Louis- 

 iana this is confined entirely to the waters of the Gulf itself. 

 Although considerable effort is being devoted to the study of the 

 early stages in the development of the shrimp, little as yet can 

 be said on the subject. Of the myriads of eggs laid, the large 

 majority must no doubt perish before they assume the adult 

 form, minus, of course, the sexual characteristics. At this time 

 they are about an inch long and from now on their history is 

 more easily traced, as they have now made their way into inside 

 waters and are abundant along the shores of lakes, bays and 

 bayous, and especially in shallow lagoons near the coast where 

 they feed in the ooze which rests upon the alluvial clay mud 

 bottoms which are bare of vegetation. Here they appear to grow 

 very rapidly and begin their slow general migration. This 

 migration seems to be in reality a gradual spread over all waters 



