326 FISHES 



water would not be sufficient for the respiration of such a dense 

 mass of large eggs. Ehrenbaum states that the male when 

 guarding a mass of spawn in this way, attached by his ventral 

 sucker to the rock, when excited throws his whole body into a 

 peculiar trembling vibration and produces a loud and distinct 

 sound resembling the rumbling of distant thunder. The spawn- 

 ing period of the lump-sucker is from January to April, prin- 

 cipally in February and March. 



The butter-fish {Centronotus or P holts gunnellus), has been 

 observed by Mr. Holt and others to roll its clump of spawn into 

 a ball by twisting its body round it, both parents taking part in 

 this proceeding. (Plate XXVII., C.) It seems certain that one 

 of the parents remains coiled round the spawn and guarding it, 

 but it has not been decided whether only the male or both 

 parents perform this duty. Professor M'Intosh of St. Andrews 

 states that he found the clumps of spawn with one of the adult 

 fishes in the holes bored in the rocks by the boring bivalve 

 Mollusc Pholas. Ehrenbaum found that in the neighbour- 

 hood of Heligoland the spawn was always found between the 

 valves of empty oyster-shells accompanied by one of the 

 parents. 



The male parent in the case of the common sand-goby 

 [Gobius minutus) makes a simple nest by scooping out the sand 

 from beneath an empty scallop-shell. The female deposits 

 her adhesive eggs on the lower surface of the shell which forms 

 the roof of the nest, and the male remains in the latter supply- 

 ing the eggs with a constant current of water by the action of 

 his pectoral fins. 



The nest-building habits of the common stickleback are 

 widely known and are easily observed. In this case also it is 

 the male parent alone which shows any solicitude for the wel- 

 fare of his offspring. He makes a nest by collecting together 

 the vegetable rubbish which is found at the bottom of the 

 stagnant fresh waters in which he lives, and arranging it in the 

 form of a round heap with a depression at the top, like a bird's 

 nest. He then seeks a female and goes through a process of 

 courtship the result of which is that she accompanies him to 

 the nest and deposits her eggs in it. Several females may 

 spawn in the same nest but they are all fertilised by the male 

 to which it belongs, and he continues to guard it till the eggs 



