Fishes. 1975 



Smooth Hound, Mustela Icevis. Common in summer and autumn 

 during the pilchard fishery. The teeth vary in form from the gene- 

 rality of the sharks, and approach those of the thornback ray in 

 their general arrangement ; and hence this species is frequently called 

 by our fishermen " ray-mouth hound." 



Picked Dog, Spear Dog, Spinax acanthias. Very abundant at 

 all seasons, In winter it retires to deep water, and feeds near 

 the ground; in summer it approaches the shores in multitudes. It 

 breeds through the summer and autumn. It brings forth its young 

 alive, and in pairs. The ova are developed in the ovaries with regu- 

 larity, there rarely being more than two of one size. The develop- 

 ment is rapid ; and by the time the young are born, two new ova are 

 ready to descend through the oviduct. In referring to the young of 

 this species, a remark may be made on a foetal peculiarity, which is 

 applicable to the young of all the British sharks and rays, but which 

 is chiefly interesting from its similarity to the foetal growth in Batra- 

 chian reptiles ; beautifully illustrating the unity of the operations of 

 nature. The young of this species, while still in utero, have the tem- 

 porary external branchiae, which are so observable in the tadpole. 

 These filaments are simple threads, varying to about three-fourths of 

 an inch in length, and are traversed by a simple reflected blood- 

 vessel : they are attached only to the anterior gills of each branchial 

 cavity : they disappear just before birth. The young are born alive, 

 and for the first few days, or perhaps weeks, when they are so weak as 

 to be unable to protect themselves, the fishermen inform me that the 

 old ones remain with them in sheltered and sandy bays, or immediate 

 neighbourhood, slowly wandering from spot to spot. The young 

 imitating the old in almost every particular. When, however, the 

 young have acquired some degree of firmness, this comparative inac- 

 tivity is exchanged for that activity and energy so characteristic of 

 the race. The old and young together, course large shoals of the 

 smaller fish with extraordinary perseverance, and on which when 

 caught the old alone can feed. This habit of joining the old ones in 

 pursuit of prey, may be called instinct, but the young are educated to 

 it from birth. I have seen this strange commixture of old and young, 

 when they have been captured with a seine, and on one occasion 

 twenty thousand were so enclosed. 



The two dorsal spines are powerful weapons of defence ; when 

 attacked, the creatures are said to bend themselves into an arch or 

 bow, and then violently to spring asunder in opposite directions. 



Hammer-headed Shark, Zygccna Malleus. A specimen of ham- 



