132 SKATES AND EAYS 



{Bala radiata) (a distinctly northern form which extends to 

 Greenland, Spitzbergen, and the north Eussian coast) sheds 

 its eggs all the year round, and Patterson has handled a female 

 ' Cuckoo Eay ' on the 4th February 1897 at Yarmouth which 

 was ' full of ova from the size of a hempseed up to chestnuts '. 

 FertiHzation takes place inside the body of the female, so there 

 is no loss at this stage. On the other hand, it is not possible 

 to argue that this family is protected by the enormous number 

 of eggs produced, as is so frequently^ and perhaps so rashly, 

 assumed in the case of other fishes. 



Incubation and Developynent 



The eggs are protected during the hatching period by the 

 leathery ' purses ' or egg cases. The writer has no information 

 as to the rate of incubation or subsequent growth, but Meek 

 writes that the young ' thornbacks ' evidently leave the egg 

 cases in summer, and both the young and adults occur in 

 inshore waters during the summer — the young fish haunting 

 depths as low as 20 fathoms. Minchin may be right in thinking 

 that large shell-fish form the chief diet of the females, and fish 

 that of the males. But the rays and skate are fairly omni- 

 vorous. A large common skate was found by Couch ^ to 

 contain two large plaice, two mackerel, a lobster, an eighteen- 

 inch ray, and half a salmon, and another caught at Mevagissey 

 was carrying by way of ballast a stone weighing about one 

 pound. 



Future Investigations 



Are skate and rays in fact being ' exterminated ' ? What 

 are the movements of the northern and southern tribes ? How 

 are spawning, hatching, and the survival of the young affected 

 by temperature and other factors ? What food do the young 

 require when they first leave the shelter of the egg cases, and 

 what are the circumstances which tell for or against a plentiful 

 supply of this food ? At what times of year do the breeding 

 fish congregate chiefly on the various deep-sea grounds from 

 Iceland to Morocco ? At what age and size does each species 

 become mature ? To what age do they survive ? And at 

 what age do they begin to deteriorate as spawners ? All these 

 things may be known, but the writer can find no answers to his 

 questions. The fishing industry has a right (indeed it is its 

 duty) to demand that the answers should be given or discovered 

 as the case may be. 



1 Bickerdyke, Sea Fishing, p. 374 (Badminton Library). 



