10 REPRODUCTION AND DEVELOPMENT OP TELEOSTEAN FISHES 



Studies of the Reproduction and Development of Tele- 

 ostean Pishes occurring in the neighbourhood of 

 Plymouth. 



By J. T. €nuniii£;ham, B.A., F.R.S.E., 



Fellow of University College, Oxford ; Naturalist to the Association. 



With Plates I. II, III, IV, V, VI. 



The following is a detailed account of the results of ray investiga- 

 tions concerning the breeding and the development, under natural 

 and artificial conditions, of some of the fishes met with at Plymouth. 

 These researches extended over the period from the beginning of 

 August, 1887, to the end of August, 1888. I have given brief 

 preliminary accounts of some of the results in No. II of the ' Journal,' 

 issued in August, 1888. As I mentioned there, the laboratory 

 work was carried on from August to November in a small room 

 hired for the purpose near the fish quay; from November to June, 

 1888, in a single room in the Laboratory without a constant supply 

 of sea- water ; after that time the Laboratory being finished all its 

 appliances were available. 



Capbos aper. 



This fish is abundant off Plymouth in the months of July and 

 August, when it is taken in large numbers by the trawlers, who call 

 it the " cuckoo." At this time it is sexually mature, and evidently 

 approaches the shore for the purpose of spawning. 



I obtained and artificially fertilized ova on August 15th, 1887, 

 when on board a trawler which fished on the east side of the 

 Eddystone, and found on my return to shore that the fertilization 

 was successful. 



The fertilized ovum of Capros aper is of a type which is common 

 to a large number of marine species ; it is buoyant, very transparent, 

 and spherical ; the perivitelline space is small, the egg-envelope has 

 no marking's on the external surface, and there is a sino-le oil-g^lobule 

 which in the normal position of the ovum is at the uppermost pole. 



