236 Proportion of the- Sex among Shrimps. 



With regard to the brown shrimp sea-coast dwellers, these 

 have been got on clean sandy ground up to twenty-five fathoms, 

 but only old and large sized specimens. The younger shrimps 

 and brood keep well to the sand-flats. With these sea shrimps 

 it may be surmised that there is a limited to and fro movement, 

 viz., from the shores to deeper water, and conversely, though 

 not necessarily a special shoaling to the estuaries. But data 

 thereon is yet too limited to establish a sound conclusion. 



FIG. 28. 



A Egg of Brown Shrimp (Cran- 

 gon vulgaris), containing 

 embryo in an advanced stage. 

 B Shrimp as hatched, in the 

 minute surface - swimming 

 Zoea stage ; no swimmerets 

 and tail end (telson) a broad 

 shovel-shaped organ. Slightly 

 modified after Kingsley. Bull, 

 Essex Inst. (U.S.), Vol. XXI., 

 1889. 



Breeding and Development. What the precise proportion of 

 the two sexes to one another are in the common shrimp is un- 

 certain. Though this much can be said, viz., that during the 

 height of the spring spawning, occasionally more than half a 

 catch in the trawl will carry berry. Moreover, those without 

 eggs, undersized shrimps, are not necessarily all males, some 

 being tardy breeding or young unripe females. The males, 

 even when fully mature, are small sized. Within our District 

 there is, so far as we are aware, but feeble indication of separa- 

 tion of the sexes into distinct squads at any season. Females 

 may be reckoned then as preponderating considerably over the 

 males.* 



* Referring to sexual characteristics, Herdman (Labor. "Rep. for 1892), does not coin- 

 cide with Ehrenbaum's representations in his " Naturgechichte von Crangon vulgaris," 

 1890. The latter important contribution we searched for in vain among the London 

 scientific libraries. Since then we managed to procure a copy direct from Berlin. 

 Ehrenbanm we find has investigated the relation of the sexes. At stations apart and 

 different months his results were conflicting the numbers of males varying from 1% 

 to 43%, and even in one instance (July) = 70% males. The percentage of females 

 carrying abdominal eggs is quite as inconstant a factor, though there is a certain 

 regularity of breeding time. Ehrenbaum's extensive researches seem to endorse the 

 view that there are periods when each sex congregates in numbers apart from the 

 other. 



