THE REPRODUCTION OF THE LOBSTER. 



67 



Ehrenbaum finds a similar state of things in the Heligoland lobster, 

 although the actual number of eggs on individuals of the same length 

 appears to be less in the European than in the American species. The 

 following table gives the German naturalist's chief results on this 

 head* : 



Total length of Lobster. 



25.4 cm. (10 inches) 

 28.1cm. (11-iV „ 



29.1 cm. (Hi 

 2P.5 cm. (HI 



29.2 cm. (11^ ,, 



31.0 cm. (12f 



31.1 cm. (12i 



35.5 cm. (14 ,, 



37.3 cm. (15 



An account of the number of eggs produced by the individual leads 

 to the consideration of what Herrick calls the " law of survival of the 

 larvffi." From the figures given for the American species, it is evident 

 that the total number of eggs produced during the entire life of a female 

 which reaches the length of 16 inches, must be very large, even should 

 Ehrenbaum's conjecture that spawning takes place only once in four 

 years prove to be correct. The question which presents itself is, what 

 proportion of this large number of eggs must develop into sexually 

 mature lobsters, in order to maintain the species in its existing 

 numbers ; and the answer to this question would be completely given 

 if we knew (1) the relation of the total number of females existing to 

 the total number of males, and (2) the number of eggs produced on the 

 average by a sexually mature female during the whole of her life ; for 

 it is only necessary that each female should give rise to two sexually 

 mature individuals in order to accomplish the result, if the number of 

 males is not greatly in excess of the number of females. 



It is known, from observation, that the males are not greatly in 

 excess, but the average number of eggs produced by females during the 

 course of their lives is more difficult to ascertain, as we have no know- 

 ledge of the number of individuals destroyed at different ages. Many, 

 no doubt, of those which lay their first brood are destroyed before the 

 eggs are hatched, whilst of those which survive, a constantly diminishing 

 number produce a second, third, or fourth lot of young. This, however. 



* In comparing Ehrenbaum's figures with those of Herrick, it must not be forgotten that 

 those of the latter author are based on an examination of nearly a thousand individuals, 

 whilst those of the former are in each case the result of counting the eggs of a single 

 female. 



F 2 



