THE BREEDING SEASON 15 



" The gonads of sea-urchins are eaten in different parts of the 

 world, and the variation in their size, corresponding with the phases 

 of the moon, is common knowledge in the fish markets of the 

 Mediterranean and elsewhere. The same fact is referred to by 

 Aristotle l and other classical writers, both Greek and Eoman." 2 



CEPHALOCHORDATA 



In the lancelet (Amphioxus 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 times. 3 



PISCES 



Among fishes the duration of the breeding season varies con- 

 siderably according to the group to which they belong. The ova 

 of Elasmobramhs 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 limited as a rule to the spring and summer 

 in temperate climates. In a single individual spawning may last no 

 longer than a few weeks or even days. 4 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 extending 

 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. 5 The investigations of the Marine Biological Association 

 have shown that in the plaice of the South Devon bays the maximum 

 spawning period is between the third week of January and the second 

 week of February. This period in the North Sea and Irish Sea 

 would appear to be slightly later. Herdman 6 records that, in the 



1 The Works of Aristotle, vol. iv., Historia Animalium, D'Arcy Thompson's 

 Translation. Oxford, 1910. And see footnote by the translator. 



2 MS. by Mr H. Munro Fox, Fellow of Gonville and Caius College, to 

 whom the author is indebted for this information. 



3 Willey, Amphioxus and the Ancestry of the Vertebrates, New York, 1894. 



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



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

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



6 Herdman, "Spawning of the Plaice," Nature, vol. Ixix., 1904. See also 

 Wallace (W.), same volume. For information concerning the spawning seasons 

 of different species of fish, The Journal of the Marine Biological Association, the 



