ZOOLOGICAL SOCIETY BULLETIN 



by the springing of new joints from the head, 

 but by the gradual division and extension of the 

 last four original segments in the long antennae, 

 the last three in the short, which eventually 

 form a many-jointed flagellum, the long anten- 

 nae at length acquiring a total of twenty-six 

 segments or more, the short antennae thirteen 

 or more. The long pair begin to divide on the 

 fifth day in some specimens, the short often 

 show no change until the fifteenth day. And 

 one antenna may not grow as rapidly as its 

 mate. It is probable that the antenna] segments 

 are of continuous growth, often broken off and 

 replaced. 



The shrimp appears to be minus the biramous 

 features so characteristic of crustaceans, except 

 for the presence of a minute accessory flagellum 

 at the third joint of the long antennae. 



The animal at birth being but 1 mm. long, 

 may have doubled its length in five days, or 

 not until fourteen days. It may be 5 mm. long 

 at thirty days, and it may measure only 4 T /2 

 mm. at sixty days, so irregular is its develop- 

 ment. 



Eyes, antennae and length of body in one 

 specimen of five and another of fourteen days, 

 or in one of thirty-six and another of sixty days, 

 may be exactly the same. Of two thirty-six 

 days old, that have lived in the same jar since 

 birth, one may have thirteen segments in the 

 long antennae, and eight in the short antennae, 

 six facets in the eye and a body length of IV2 

 mm., while another may possess twenty-one seg- 

 ments in the long, and ten segments in the short 

 antennae, an eye wholly fused as in the adult. 

 and a body length of fi mm. The most rapidly 

 developing specimen under observation attained 

 a length of 7 mm. in 52 days. At the same 

 time, one 78 days old measured but 5 mm. 



The question has been asked the Aquarium, — 

 Are fresh-water shrimps inimical to young fish- 

 es? A statement was printed some time ago to 

 the effect that they will fasten in numbers upon 

 small, living fishes, and eat them piecemeal. 

 This is a difficult accusation to verify, first be- 

 cause an active fish in an aquarium consumes 

 the shrimps fast enough to prevent being set 

 upon by them : and secondly, because the 

 shrimps are cannibals, and if segregated until 

 hungry enough to attack a live animal, the 

 stronger will devour their own weaker brothers 

 and spoil the experiment. When one evidences 

 weakness, another seizes it — usually by the head, 

 though occasionally the tail end is selected — 

 and begins to eat it up. Or two may attack. 

 one the head, the other the tail, and act as if 

 they would tear their victim apart. The body 

 of the seized one usually turns pale at the first 



bite, a curious fact whose psychological or physi- 

 ological basis we are not prepared to discuss. 

 Cannibalism is a slow process of extermination, 

 for the animal kicks and breathes feebly even 

 after its head is gone. The shrimps annoy pond 

 snails, possibly if hard pressed for food would 

 devour these mollusks alive ; and no doubt a 

 small disabled fish would fall prey. But a 

 healthy, hungry fish certainly ought to have the 

 odds in its own favor. 



While this paper presents more than has hith- 

 erto been recorded regarding fresh-water 

 shrimps, there are some things still left for fu- 

 ture investigators to determine : how often they 

 molt, how often they breed, how the eggs are 

 fertilized, the exact period of incubation, how 

 long they would live if protected from enemies 

 including cannibals, whether males occur in ev- 

 ery generation, etc. Other points of interest 

 would, of course, arise upon a more extended 

 study of these interesting animals. 



THE INCREASING POLLUTION OF 

 STREAMS. 



By C. H. Townsend. 



THE American Fisheries Society, at a re- 

 cent meeting in New York City, lasting 

 several days, devoted several sessions to 

 the subject of water pollution as affecting the 

 fisheries. It was shown beyond doubt that dur- 

 ing recent years the pollution of streams has 

 increased enormously and that there is great 

 need for concerted action in dealing with it. 

 Corporations and individuals should co-operate 

 with state and national fishery and health 

 boards, and a campaign of education should be 

 arranged for. 



The subject has many bearings: the loss of 

 food fishes, the destruction of spawning grounds, 

 the abandonment of fishery industries, the men- 

 ace to public health, the contamination of city 

 water supplies, the loss of chemical by-products, 

 the injury to property, the accumulation of deep 

 beds of sludge in harbors, the unsightliness of 

 polluted streams, etc., etc. 



The reports of various state fishery boards 

 are burdened with the evils of water pollution 

 by sewage and factory wastes. In spite of the 

 existence of statutes broad enough to meet most 

 of the conditions, little headway is being made. 

 It is not our national habit to begin reforms 

 when serious results are threatened, but rather 

 after trouble has actually arrived. 



The decline of the shad fishery in the Hud- 

 son River is attributable chiefly to pollution 



