12 



thick, slightly coiled tubes leading from the lower side of the 

 central mass to the external openings in the basal segments of 

 the last pair of legs. The terminal portion of the duct is much 

 enlarged and nearly fills the basal segment. As already men- 

 tioned, it becomes very conspicuous at the breeding season. Dur- 

 ing the breeding season the sperm ducts are swollen and filled 

 with the milt, a thick viscous fluid, the greater part of which is 

 made up of sperm. The sperms, the vital part of the milt, are 

 small, roundish bodies, witha short process on one side. At the 

 time of mating the sperm are formed into masses called sperma- 

 tophores and are attached to the ventral surface of the female 

 (in a 'crude pouch or pocket between the bases of the legs) by 

 the tubular part of the first pair of swimmerets. It is probable 

 that the enlarged terminal portion of the sperm ducts enter into 

 this transferrence in some manner; but, as the mating has not 

 been observed in this form, the exact way in which this takes 

 place is not known. 



The fertilization of the eggs (i. e., the fusion of the sperm 

 and the egg) takes place as the eggs are extruded from the ovi- 

 ducts, usually some time after mating. 



EGG LAYING HABITS. 



In the majority of the shrimp the female carries the eggs dur- 

 ing their development attached to the under side of the abdomen, 

 between the swimmerets. Females in this condition, or in 

 ' ' berry, " as it is sometimes called, are shown in Plate "V, figures 

 1-2. The group of shrimp to which the "Lake Shrimp" belongs 

 (Penaeidae) , however, differs from the others in this respect, 

 and it is claimed that the eggs are not attached to the swimmer- 

 ets of the female during development, (a) The eggs are merely 

 set free into the water and allowed to shift for themselves during 

 development. This means that they are at the mercy of the cur- 

 rents in the water or may fall easy prey to any of the predaceous 

 forms living in these regions. On this account many more eggs 

 are produced by each female than would be in those forms which 

 protect the egsrs by carrying them during the early development. 

 The eggs are also rather small and undergo their early develop- 

 ment floating around at the surface of the water. In this con- 



fa) Rathbun, Bull., 4 S. F. C. 1900. Vol. 2. page 100. 



