33 



examination in the laboratory of more than 560 Shrimps 

 is that they are chiefly carnivorous in their diet. We find 

 in their stomachs : — Crustacean remains, such as Amphi- 

 pods, small Crabs, young Shrimps, and Copepoda ; also a 

 considerable amount of Molluscan remains, such as small 

 specimens of Scrobicularia alba, Cardiiim edide, and 

 Tellina balthica. Annelids must also form a fair pro- 

 portion of their food from the number of Polychaete setae 

 in the stomachs, with occasionally fragments of the tube 

 of Pectinaria, and the horny jaws of a Nereid. More 

 rarely the stomachs contain Foraminifera and small spines 

 of Echini ; and sometimes green seaweeds, minute filam- 

 entous and microscopic Algae and Diatoms. We find from 

 experiments on them in captivity that Shrimps will also 

 eat practically any animal matters such as pieces of dead 

 fish, other Shrimps, beef, &c. 



The male Shrimps are less numerous, and are much 

 smaller than the females, and so are comparatively rarely 

 caught in the nets. It is a difficult matter to determine 

 the sex in small specimens, and we find that even in fully 

 formed sexually mature individuals the inner branches of 

 the first abdominal appendages, which are the only exter- 

 nal sexual characteristics to depend upon, do not show the 

 markedly different conditions figured by Ehrenbaum.* We 

 give now on Plate II. some figures showing: — (fig. 1) the 

 entire second abdominal appendage of a large female 

 Shrimp (2| in. long) ; and (fig. 2) the entire first abdominal 

 appendage of the same Shrimp to show the modification of 

 the endopodite or inner branch (en.) which is shown more 

 highly magnified in fig. 3, in the adult female; also (figs. 

 4 and 5,) the fully formed endopodites of the same 

 appendage from two adult males (1J ins. long); while fig. 6 

 * Zur Naturgeschichte von Crangon vulgaris. Berl. 1890, Taf. II., figs. 

 15 A & B. 



