COURTSHIP AND NURSERY DUTIES. 119 



wind blow shorewards with abnormal strength 

 and duration, and untold millions of unhatched 

 cod may perish, or let the temperature, for a ftw 

 weeks during the summer months, be abnormally 

 low, and the same fate may overtake hosts of 

 embryonic gurnards. Under such conditions it 

 is only by the selection of suitable spawning- 

 sites, a prolongation of the spawning-time (on 

 the principle of not putting all the eggs in one 

 basket), and other devices, that the pelagic spawn- 

 ing fishes have held their own." 



The floating, or pelagic eggs, it is interesting 

 to note, are provided with an oil globule which 

 serves to diminish their specific gravity. But it 

 would seem that under certain conditions, as yet 

 unexplained, the specific gravity of pelagic eggs, 

 relative to sea-water, may undergo sudden changes 

 resulting in a sinking or rising. Thus eggs 

 which normally are found only floating at the 

 surface, may occur floating some distance below 

 this, in mid- water, or deeper, even on the bottom. 

 In the Baltic, according to Mr Masterman, *' the 

 eggs of the plaice have been found far below the 

 surface, floating underneath the stratum of 

 brackish water." The egos of the common eel 

 again, which are deposited in the deep sea in 

 250 fathoms of water, remain suspended in the 

 water at that depth, and there hatch (see 

 p. 129.) 



One of the gobies (Latrunculus pellucidus), 

 common on the coasts of the British Islands, 

 is remarkable for the fact its whole life's course 

 is run in a single year. In June, July it deposits 

 its eggs, these hatch in August, by December the 



