16 THE PHYSIOLOGY. OF REPRODUCTION 



Scotland, it has been observed to spawn at the same time. The 

 sea-urchins at Naples spawn at the end of the year (E. acutus 

 being mature in November and December, and E.mwrotuberculatus 

 from September onwards). ^ 



Cephalochoedata 



In the lancelet {Anvphioxus lanceolatus) of the Mediterranean 

 the breeding season extends from spring until autumn, the 

 glands becoming so large by the ripening of ova and spermatozoa 

 that the atrium is used up to its utmost capacity. Spawning, 

 when it occurs, invariably takes place about sun-down {i.e. 

 between .5 and 7 p.m.), and never, so far as known, at any 

 other time.^ 



Pisces 



Among fishes the duration of the breeding season varies 

 considerably according to the group to which they belong. 

 The ova of Elasmobranchs are deposited singly or in pairs at 

 varying intervals throughout a great part of the year. In 

 Teleosts, on the other hand, the breeding season is hmited as a 

 rule to the spring and summer in temperate chmates. In a 

 single individual spawning may last no longer than a few weeks 

 or even days.' The enormous number of eggs produced by 

 most Teleosts must be connected with the absence of internal 

 fertilisation, involving a large wastage of ova which never come 

 in contact with male cells or spermatozoa. 



The cod, off our own coasts, has a spawning season ex- 

 tending from January to June, but the majority of individuals 

 spawn in March. It has been found, however, that in some 

 parts of the North Sea the cod may spawn in the autumn. In 

 the whiting the spawning period lasts from early March until 

 the third week in August.* The investigations of the Marine 



• Lo Bianco, loc. cit. The spawning times of most of the Naples 

 Echinoderms are given iii these memoirs. 



" Willey, Amphioxus and the Ancestry of the Vertebrates, New York, 

 1894. 



3 Bridge, "Fishes," Camb. Nat. Hist., vol. vii., London, 1905. 



• Masterman, "A Contribution to the Life-Histories of the Cod and 

 Whiting," Trans. Roy. Soo. Edin., vol. xl., 1900. 



